In the prologue, beyond the territory of the four Clans, WindClan is seeking a home after having been driven out of the forest by Brokenstar. Ashfoot voices her concern about the safety of her kits, so Tallstar sends his deputy Deadfoot and the warrior Onewhisker out to look for shelter. A few moments later, they return, having found a tunnel WindClan could live in. Tallstar reluctantly leads his Clan into their new refuge.
Meanwhile, Fireheart and Graystripe have just finished their warrior vigil. Graystripe says that he could sleep for a moon, prompting Tigerclaw to show up and call him lazy. Fireheart remembers Ravenpaw's words about Tigerclaw being a murderer, and he decides to tell Bluestar about it. Just then, Bluestar holds a ceremony. She gives Longtail an apprentice named Swiftpaw, and Longtail is overjoyed.
On the night of the next Gathering, Fireheart talks to Bluestar and tells her that Ravenpaw isn't dead. However, she doesn't believe him when he says that Tigerclaw killed Redtail. Fireheart is frustrated, and decides to keep trying to convince her of Tigerclaw's evil. At the Gathering, Nightpelt has become ShadowClan's leader. He declares that ShadowClan will be hunting in WindClan's empty territory. Crookedstar decides that RiverClan will hunt there as well. Bluestar protests, so Nightpelt challenges her to bring WindClan back to the forest.
Back at the camp, Bluestar decides to take Nightpelt up on his challenge. She gives Graystripe and Fireheart a mission: Track down WindClan and bring them back to the forest. After getting travelling herbs from Yellowfang, the two head to WindClan territory. They find the camp, and manage to locate WindClan's tunnel, despite nearly running into Nightpelt (who was on the way to the Moonstone to receive his nine lives) on the way there.
After Fireheart explains that Brokenstar has been driven out, WindClan agrees to return with him. Fireheart has a harrowing experience trying to get a kit named Gorsekit across the Thunderpath, but in the end the group makes it to Barley's barn. There they find Ravenpaw, and Fireheart notes that he seems much happier than he ever was in ThunderClan.
The next day, the cats start their journey back to the WindClan camp. Barkface shocks everyone when he reads a sign from StarClan saying, "This day will bring an unnecessary death." However, they make it back to WindClan camp without trouble. Tallstar sends Deadfoot and Onewhisker with Fireheart and Graystripe to keep them safe on the way back from WindClan camp. They decide to take a shortcut through RiverClan territory, but Leopardfur doesn't like this, and she orders a patrol of cats to attack. A group of ThunderClan warriors arrive to help out, and the battle rages. Fireheart saves Sandpaw from falling off a cliff, but Graystripe's opponent Whiteclaw takes the plunge and dies. A grief-stricken Leopardfur calls off the battle after swearing revenge, while Fireheart realizes that Whiteclaw was the unnecessary death Barkface spoke of.
Back at the camp, Bluestar decides to make Fireheart and Graystripe into mentors. She gives them the kits they rescued from Brokenstar back in Into the Wild. Fireheart gets the energetic Cinderpaw, while Graystripe gets the thoughtful Brackenpaw. Fireheart spies a she-cat in the woods while training Cinderpaw, and later realizes that it was his sister, Princess. The next day, Fireheart gets Graystripe to train Cinderpaw while he goes to visit Princess. They talk for a little while, and Fireheart leaves feeling elated. Tigerclaw confronts Fireheart over this, but he manages to talk his way out of the conversation.
A few days later, Fireheart and Graystripe take their apprentices out together for training. Graystripe tries to catch a vole on thin ice, and he nearly drowns. However, a pretty RiverClan warrior saves him. Fireheart takes him back to the camp. Yellowfang says that Graystripe has a cold, and will have to stay in the camp for a while. Fortunately, Runningwind is happy to lend a paw and train Brackenpaw.
After a RiverClan patrol is spotted lingering around Sunningrocks, Tigerclaw worries that they will try to retake it. To make sure the Clan is strong enough to defend itself, Cinderpaw and Brackenpaw have to partake in an assessment. Fireheart notes that they're doing well, and Cinderpaw asks him about his kittypet roots. Fireheart worries that he isn't devoting his loyalty to his Clan. However, soon he is given other problems to worry about. Graystripe hasn't been getting better, and Fireheart realizes that this is because he is sneaking out of the camp. Leaving Cinderpaw and Brackenpaw with Runningwind, Fireheart shadows Graystripe and finds his friend having a covert meeting with the RiverClan warrior who saved him from drowning. Enraged, he confronts them, and learns that the RiverClan warrior, named Silverstream, is Crookedstar's daughter. Graystripe and Silverstream gang up on Fireheart, telling him not to interfere with true love.
Fireheart leaves the meeting feeling flustered. He talks with Yellowfang and learns that Bluestar is on the verge of losing another life. If she dies, then she'll only have one life remaining. Tigerclaw shows up and tells Fireheart that Bluestar needs to go to the Thunderpath and fall into his obvious trap. Bluestar is too sick to go, so Cinderpaw volunteers. Fireheart tells her to stay in the camp, and grabs some catnip for Yellowfang. However, Cinderpaw disobeys his orders, and Fireheart finds her broken body by the Thunderpath.
Tigerclaw helps Fireheart take Cinderpaw back to the camp. There, Yellowfang says that there's a slight chance that Cinderpaw will live, but she'll never be a warrior. Fireheart, overcome with grief at his failure as a mentor, heads back to his den to get some sleep. There, Graystripe's love of Silverstream makes him feel compelled to insult Fireheart.
Fireheart talks to Princess, explaining the situation. Princess points out that Tigerclaw was probably attempting to lure Bluestar into his trap, and Fireheart agrees. He takes some catnip back to the camp. Then, he decides to apologize to Frostfur because he failed her daughter Cinderpaw. Frostfur decides to snap Fireheart out of his depression, and he tries to find a way to move forward.
Tigerclaw sends Fireheart and Sandpaw out on a border patrol together. Fireheart expects Sandpaw to act venomous like usual, but she acts friendly instead. The two notice that the river is frozen, and back at the camp Sandpaw explains her plan for a raid on RiverClan. Graystripe tags along, desperate to protect Silverstream from his Clanmates. However, the river has already started to thaw by the time the ThunderClanners get there, and a raid is impossible. Graystripe decides to attack Fireheart instead, but Bluestar stops him.
Fireheart goes back and meets Princess, who has a kit with her. She explains that it's her firstborn, and she wants him to be wild and free. Fireheart takes the kit to be raised by ThunderClan. Bluestar names him Cloudkit, and Brindleface takes him in because she had lost two of her own kits.
Fireheart goes to see Cinderpaw, and she wistfully recalls the days when he trained her. Fireheart is worried about how the Clan will react to Cloudkit, but Cinderpaw points out that Fireheart has turned his kittypet roots into strength. Fireheart is called away, and he heads off to the Gathering. Onewhisker talks with him, mentioning the WindClan is settling in well. However, not all of the cats are happy. Nightstar angrily rants about how strange scents are being found on ShadowClan territory, and accuses the other Clans of leaving them. Back at the camp, the ThunderClan warriors worry that if they are seen as allies of WindClan, ShadowClan and RiverClan will form a Clan alliance and declare war.
A few days later, every single warrior in ThunderClan leaves the camp except Fireheart. He worries about how he's all alone, before realizing that Brokenstar's rogues are hanging around the forest. Fireheart gathers up all the apprentices and elders to defend the camp, just as Brokenstar bursts in. Fireheart sees Clawface, and his grief over Spottedleaf's death sends him into a frenzy. He attacks Clawface, but the rogue is too strong. Just when it looks like Fireheart will die, Graystripe returns to the camp and kills Clawface. Yellowfang blinds Brokenstar, and Fireheart stumbles upon her lamenting that she can't kill Brokenstar because he's actually her son. The rogues are driven off, but Bluestar decides to make Brokenstar an elder. The ThunderClan cats change his name back to Brokentail to show that he is no longer leader.
For their valour in battle, Bluestar makes Dustpaw and Sandpaw warriors, giving them the names Dustpelt and Sandstorm. However, the triumph is short-lived, as Cloudkit and the other kits have disappeared from the camp. Fireheart tracks them down, and it turns out that they wanted to help the camp with hunting. Cloudkit has caught a big piece of fresh-kill, so Bluestar lets him off with a scolding.
Spottedleaf comes to Fireheart in a dream and warns him to beware a warrior he cannot trust. Fireheart worries that he can't trust Graystripe.
Fireheart wakes up and leaves his den just in time to see Onewhisker burst in. Onewhisker explains that ShadowClan and RiverClan have teamed up to attack WindClan. The ThunderClanners rush off to help WindClan, finally deciding to form a Clan Alliance with them.
Graystripe defeats Wetfoot in battle, while Fireheart takes on Leopardfur, RiverClan's deputy. Leopardfur gets Fireheart in a death-grip, and he yells for a nearby Tigerclaw to help him. Tigerclaw smirks and watches as Leopardfur finishes Fireheart off.
And then Fireheart ninja-kicks Leopardfur halfway across a clearing. Seriously.
Fireheart then fights Silverstream and nearly kills her. However, he spares her after seeing a horrified Graystripe nearby. Fireheart and Runningwind beat Nightstar up, while Tigerclaw finishes the battle by defeating Crookedstar.
Tigerclaw confronts Fireheart over sparing Silverstream, but nothing comes out of it. However, a thankful Graystripe apologizes for his treatment of Fireheart. The two warriors renew their friendship as they shelter from a raging storm.
Tropes that appear in this book:
- Abandoned Area: During their journey home, Fireheart, Graystripe, and WindClan shelter in an abandoned Twoleg nest.
- Accidental Murder: Whiteclaw falls to his death over a skirmish between his home Clan (RiverClan) and ThunderClan over Sunningrocks. He was fighting Graystripe of ThunderClan along the edge of the gorge and he slips, grabbing onto the side. Graystripe attempts to save Whiteclaw but he still falls to his doom.
- Amateur Sleuth: Fireheart spends part of the book investigating Redtail's death.
- American Kirby Is Hardcore: The French title for Fire and Ice roughly means In Fire and In Blood.
- Belated Backstory: Yellowfang doesn't have her backstory explained until this book.
- Betrayal by Inaction: Fireheart's suspicions about Tigerclaw being a traitor are confirmed when, during a battle, Fireheart is pinned down by Leopardfur, who is trying to kill him. He calls to Tigerclaw for help, but Tigerclaw ignores him and just stands there watching it happen.
- Big Damn Heroes: Graystripe shows up just in time to save Fireheart from Clawface.
- Braving the Blizzard: Cloudkit sneaks out of camp to go hunting during a blizzard even though he's not old enough. As a result, Firestar and Sandstorm need to brave the weather in order to find him.
- Bring Help Back: A WindClan cat runs to ThunderClan to bring them back to help, since the other two Clans are trying to drive them out again or kill them.
- Career-Ending Injury: Cinderpaw is permanently crippled after being hit by a monster on the Thunderpath, and she is unable to become a warrior when it becomes clear that it will never heal properly.
- Child of Forbidden Love: Yellowfang reveals that Brokenstar is her son; she'd fallen in love with Raggedstar, which was forbidden to her as she is a medicine cat.
- Child of Two Worlds: Fireheart feels torn between loyalty to his kittypet sister and his loyalty to the Clan.
- Dark Is Evil: The villainous cats Tigerclaw and Brokenstar are dark brown.
- Death of a Child: One of Brindleface's kits dies of sickness, and it is noted that she also had lost one in the litter shortly after they were born.
- Dishonored Dead: Normally when a Clan cat dies, there are traditional funeral rites, which involve a medicine cat speaking ceremonial words, and their Clanmates sharing tongues and keeping a night-long vigil by the body, with a burial by the elders in the morning. When Clawface, a ShadowClan warrior turned rogue, is killed on a raid on the ThunderClan camp, his body is buried without ceremony as punishment for his crimes.
- Disney Villain Death: Whiteclaw falls into the gorge and dies.
- Early Installment Weirdness:
- In this book, "Clan mate" is two separate words; in later books, it becomes one word ("Clanmate").
- It is mentioned in this book that warrior fathers don't stay close to their kits and specifically notes Silverstream and Crookedstar as a rare exception. This is supported by the other characters' behavior; for instance, most of the first series characters have no real relationship to their fathers; in fact, the authors didn't bother deciding on who the fathers even were for most of them. This changes later in the series; in fact, by the third series, one character who had kits as the result of a one-night stand (which itself is rare later on) is criticized by other characters for not wanting to play with his kits.
- In this book, Tigerclaw suggests that Darkstripe and Longtail be given a second apprentice each, and Bluestar replies that she considered it. Aside from one cat later asking to take on the she-cat he likes as a second apprentice - which is mostly played for laughs - theres no other reference in the series to cats being the official mentor to more than one apprentice at a time.
- Embarrassing Rescue: Fireheart saves Sandpaw from falling into the gorge. Considering that up until this point Sandpaw has done nothing but insult Fireheart and call him useless, it's not surprising that she's angry at him for saving her - and pretends that she didn't need the help.
- Eye Scream: Brokenstar gets his eyes clawed by Yellowfang and is permanently blinded.
- Fire/Ice Duo: The title of the book is Fire and Ice. It may be referring to the main character Fireheart, and possibly the winter season the book takes place during, or it may be a metaphor for the conflicts in the book.
- First Snow: Fireheart experiences his first snow in this book. At first he is amazed because he hasn't seen it before; he was shut inside as a kit still living with Twolegs when it last snowed. He quickly learns that snow makes it difficult to move around, however.
- Gender Bender: One-Eye is briefly mentioned as male in the scene after the Gathering where Nightpelt reveals himself to be leader."But his name - hasn't he been accepted by StarClan yet?" asked One-Eye.
"He plans to travel to the Moonstone tomorrow night," Tigerclaw told him.
- Incurable Cough of Death: Greencough rages through the camp; Bluestar even loses a life to it.
- Love Across Battlelines: Graystripe and Silverstream's romance. Inter-Clan romances are banned specifically because they lead to the conflict of loyalty to Clan vs. loyalty to mate in a battle.
- Make It Look Like an Accident: Tigerclaw tried to trick Bluestar into running onto the Thunderpath by saying he had an urgent message and leaving his scent too close to the edge, at a spot where the verge was very narrow. Bluestar ended up being too ill to go, however, and Cinderpaw took it upon herself to go in her place and ended up being badly injured.
- Malicious Misnaming: When Fireheart is punished by having to temporarily live like an apprentice (having a warrior supervise him at all times and sleep in the apprentices' den), Longtail doesn't miss the opportunity to mock Fireheart and calls him by his apprentice name, "Firepaw".
- Meaningful Rename: Sandpaw and Dustpaw earn their warrior names, Sandstorm and Dustpelt.
- Mentor Archetype: Although she isn't his mentor in the sense the series usually uses the word (training the character to be a warrior or medicine cat), Yellowfang serves this role to Fireheart; she's the elderly, dear friend he always goes to for advice.
- The Missing Faction: WindClan is this at the start of the book, since they'd been driven out of their territory partway through the previous book. RiverClan and ShadowClan are pleased at the extra hunting territory at first, but Bluestar convinces the other leaders that it's wrong and gets them to agree that the Clan should be brought back.
- Murder by Inaction: In the battle at the end, Tigerclaw sits and watches without helping as Leopardfur nearly kills Fireheart. Fireheart is so furious about it that he finds the energy to push her off him.
- Names to Run Away from Really Fast: Colors: Whitecough is the name of a sickness similar to a cold. Greencough is a deadly, contagious sickness.
- The Noun and the Noun: Fire and Ice.
- A Pet into the Wild: Fireheart brings his nephew Cloudkit, a house cat, to ThunderClan to live.
- The Plague: Greencough, a deadly, contagious pneumonia-like sickness.
- Red Sky, Take Warning: The morning that WindClan arrives home, their medicine cat, Barkface, announces that the clouds are stained with blood, and the day will bring an unnecessary death. This comes true when Fireheart and Graystripe head home — rather than taking the long way around RiverClan territory to get home like they're supposed to, they take a shortcut through it. A patrol spots them and starts a fight, and one of the RiverClan warriors dies when he falls into the gorge.
- Rescue Romance:
- Silverstream rescues Graystripe from drowning, and he's barely out of the water before he's flirting with her. Bonus points for being Star-Crossed Lovers.
- Fireheart stopped Sandpaw from falling into the gorge, and it was from then that her feelings about him clearly began to change.
- Secret Relationship:
- Graystripe and Silverstream, as they are from different Clans.
- Yellowfang reveals that she fell in love with Raggedstar, but that she had to keep the relationship and the fact that she was Brokenstar's mother secret, due to her being a medicine cat.
- Separated at Birth: Fireheart was born as a house cat, so he and his siblings were split up and all given to new owners when they were still kits. After living in the forest Clans for a few moons, he is patrolling the edge of his territory one day and spots his sister. She doesn't recognize him at first, but they quickly become friends again and he begins to regularly visit her.
- Series Continuity Error: In Into the Wild, Bluestar tells Darkstripe that he's ready for his first apprentice. However, in Fire and Ice, when Longtail gets an apprentice, Bluestar says that Darkstripe was his mentor.
- Shame If Something Happened: There's one moment where Cloudkit loses the moss ball he was playing with, and Tigerclaw gives it back to him, saying "Be careful. You wouldn't want to lose such a precious plaything." He looks at Fireheart while saying this, however, and Fireheart realizes the implication that his nephew Cloudkit is the "plaything".
- Sick Episode: Several ThunderClanners start coming down with the cold-like illness whitecough and the more deadly disease greencough.
- Sneaky Departure:
- Tigerclaw claims to have found evidence of an invasion that the Clan leader Bluestar needs to see. (It's actually a trap he set to kill Bluestar so that he can take over.) However, Bluestar is too sick to go and see, so Fireheart's apprentice Cinderpaw offers to go instead. Fireheart forbids her from going, but she sneaks out of camp anyway and walks into Tigerclaw's trap, causing her to get hit by a car and break her leg.
- Graystripe constantly sneaks out of ThunderClan's camp so that he can meet with his love interest Silverstream. This is necessary, as they are in a forbidden relationship.
- Star-Crossed Lovers: Graystripe and Silverstream, who are from different Clans.
- Too Desperate to Be Picky: Clan cats will only shelter in abandoned buildings when absolutely necessary; one example is in this book when a storm kicks up as WindClan travels home.
- Took a Level in Kindness: Sandstorm used to be such an Alpha Bitch to Fireheart when he joined ThunderClan. After he saves her from falling over the gorge, she becomes a better cat and falls in love with him. But she still has her snarky moments, however.
- Tricked to Death: Tigerclaw attempts this by sending a message that he wants Bluestar to meet him in a spot where he claims ShadowClan was scented on their territory, and setting his scent marker close to the edge of a road so that she'd run out onto it. Cinderpaw was caught instead, but thankfully didn't die.
- Unwanted Rescue: Fireheart realizes that Sandpaw and the enemy warrior that she's fighting are about to fall into the gorge, so he knocks the other warrior away from her (and from the edge) and pulls Sandpaw off the edge and to her feet. Sandpaw's furious at him for "saving" her from the enemy warrior because she already dislikes Fireheart and insists she can fight her own battles, but just then another cat falls over the edge and drowns. That makes Sandpaw realize what Fireheart had actually been saving her from, and she grows more friendly toward him from then on.
- Uriah Gambit: Tigerclaw suspects that Ravenpaw told Fireheart what he had seen. During battle, when Fireheart is fighting for his life and calling for help, Tigerclaw just sits there and watches; fortunately Fireheart manages to fight his way out.
- Vagueness Is Coming: Many prophecies in the series vaguely foretell destruction and danger without actually managing to tell the Clans what exactly is coming. This includes the one in this book: "A battle is coming, Fireheart. Beware a warrior you cannot trust."
- Villain with Good Publicity: Tigerclaw. Firestar and Graystripe are the only characters in all of ThunderClan who suspect that he could be treacherous.
- Wham Line: From Yellowfang (about why she can't kill Brokenstar): "He is my son."