In the prologue, an unknown black tom has a vision of worried cats gathered around a sick tom, and he is then visited by starry cats who tell him that he is special to them, that strangers will come to his home, and that he should let said strangers guide his paws. He awakens, convinces himself it was just an ordinary dream, and falls back asleep.
The book itself opens an unspecified (but not long) amount of time after Shattered Sky, the third book of A Vision of Shadows. SkyClan has moved into the forest, establishing a territory in between ThunderClan and ShadowClan using some of the latter's territory. Twigpaw is mentioned to have joined SkyClan along with her father and sister, but is still in training since she's learning her new Clan's methods. ShadowClan is extremely weak; their numbers have dwindled, and the remaining cats have little confidence in each other and especially in their leader, Rowanstar.
Tigerheart, ShadowClan's deputy, races through the forest to meet with Dovewing: during his time as a refugee in ThunderClan, their former love had rekindled, and they've since been meeting in secret in SkyClan's new territory. Dovewing reveals that she's expecting his kits, and that she'd had a dream that she's certain is a sign: the nursery is empty and shadows grow, and she wakes up filled with dread. She's also dreamed about a Twolegplace and a roof with sharp points, and is convinced that something will happen to their kits unless they leave the Clans and go there. Tigerheart doesn't want to leave, since his Clan needs him, and tries to get her to stay, but she gives him an ultimatum: she is leaving in three days with or without him.
Over the next couple days, he tries to decide what to do. Willowshine visits and announces that she's had a vision that they need to find a six-toed cat to fend off "the coming storm", and Puddleshine also reveals to Tigerheart and Rowanstar that he had a vision: the sun – and therefore the shadows - gradually fading, and Tigerheart is convinced that it's about Rowanstar and the fate of ShadowClan. Ultimately he decides to go with Dovewing but gets delayed, and realizes that she's left without him – but then sees Puddleshine's vision himself, and decides he needs to stay for the sake of his Clan.
Things don't go so well over the next few days: prey is scarce, and they nearly get into a fight with SkyClan over a rabbit Tigerheart let them have. Rowanstar, after scolding Tigerheart, offers to step down for him to become leader, but Tigerheart declines the offer, still thinking about Dovewing. In the end, despite Puddleshine having a vision of Tigerheart casting the greatest shadow of all, Tigerheart sets off to find his mate.
Along the way, he meets a trio of kittypets: one of them, Ajax, once lived in the Twolegplace Tigerheart is searching for. They tell him that the "Thundersnake" (train) will take him there, but he insists upon walking and following the Silverpath it travels upon. Along the way he finds a tuft of Dovewing's fur, so he knows he's going the right way. Due to hiding among luggage at one of the stops later however, he finds himself actually trapped on the Thundersnake, and it brings him into the Twolegplace.
There's a loner living at the station, and Tigerheart helps him scare off some bullying rogues. He later encounters another group (which later most frequently gets called "the guardian cats"), which lives in an abandoned Twoleg nest - and finds Dovewing with them. Many of the cats are healers, and they all care for the sick and injured that come through – the best healer is Spire, a black tom who seems to have strange dreams like a medicine cat, who seems to be expecting them. Other cats hunt and scavenge, and some are primarily guardians, though they do not have formal training of any sort. They've been having trouble with a pair of foxes keeping them from their herbs, but with Tigerheart teaching them some fighting moves, they manage to drive the foxes away.
Dovewing and Tigerheart settle into the easy life of the city cats until Dovewing's kits come (one moon early, but no problems): two she-cats, Lightkit and Pouncekit, and a tom, Shadowkit (who was named after Tigerheart's Clan, and who, Spire claimed, would "see into the shadows"). They choose to wait until their kits are strong enough to travel to bring them back to the Clans. As leaf-fall turns to leaf-bare, Tigerheart can't help but wish for the life of a warrior: all the city cats, both the guardian cats and strays, see themselves as little more than scavengers. A new gang, led by a she-cat named Fog, moves in and starts to scavenge and stay nearer and nearer to their home, even interfering with them gathering food, but the guardian cats refuse to mark a territory like the Clans, insisting that life works differently in the city.
Tigerheart learns that Fog and her gang were driven out of their home by foxes (the very ones they'd fought in order to defend the guardian cats, most likely) and figures that the best way to get her gang out of the guardian cats' fur is to once again fight the foxes and chase them away. He knows the guardians alone are not enough (Fog refuses to help) but gets the idea to lure them into the Twoleg traps that have recently been springing up around the city. With the help of one of Fog's cats, they are successful, and peace between the groups is established.
The kits grow enough to start becoming a pawful, trying to explore on their own. Spire has a vision about "shadows fading", and Shadowkit's had one about a cat that looks like Ivypool with kits, and Tigerheart and Dovewing decide to return to return to the Clans with their kits. Several of the guardian cats come as well to join the Clans: Spire and his kit assistant Blaze, and two cats named Cinnamon and Ant. The station cat, Dash, helps them out of the city and into the wilderness. Spire has a vision along the way that they need to follow "the orange sun". He vanishes that night, and they find him by a building with a round orange circle on it, and with him some ShadowClan warriors that had been missing since the fight with Darktail: Rippletail, Sparrowtail, Cloverfoot, and a very pregnant Berryheart. They had fought on Darktail's side and have come to regret it, and hope for forgiveness and to be able to return to their Clan.
After a near-miss with a Thundersnake, when Spire saves Lightkit's life, the tom insists they must leave the Silverpath or else there will be meaningless deaths, and they choose to trust his visions and dreams. They cross a Twoleg bridge after, which starts to open in the middle when Pouncekit is crossing, and Spire manages to get the kit to safety before falling into the gap. The patrol grieves and decide to honor him as a ShadowClan warrior; Tigerheart speaks words to StarClan, renaming him Spiresight, and they sit vigil. Berryheart has her kits that night, and names them Hollowkit, Sunkit, and Spirekit.
Two moons after they'd left the city – a moon after the birth of Berryheart's kits – Shadowkit has a dream about how to get home. They leave a quarter moon after that, when Berryheart feels her kits can travel. Shadowkit just finishes telling Tigerheart that he has a bad feeling that they should have left already, when an owl swoops, aiming for one of Berryheart's kits. Tigerheart fights it and ends up getting lifted into the air and dropped, resulting in something breaking internally, which nobody knows how to fix. Due to Shadowkit's vision, they know they're close to the lake, and help him along the best they can, but he's barely conscious and eventually he gives in to sleep.
He awakens in what he knows to be StarClan. He meets Spiresight there, who shows him the patrol carrying his body and tells him that it's not his time to die yet. Rowanstar – in StarClan himself, and insisting that he be called Rowanclaw again for an unknown reason – tells Tigerheart that there's one way a cat can be sent back, and Tigerheart realizes that it's through a leadership ceremony. He receives nine lives (though is told that he's already used one up due to the manner in which he's receiving them – much like what happened with the first leader, Windstar): Rowanclaw (strength), Kinkfur (courage), Pinenose (compassion), Dawnpelt (hope), Yellowfang (forgiveness), Sagewhisker (persistence), Littlecloud (acceptance), Raggedstar (loyalty), and Flametail (love). StarClan gives him his new name, Tigerstar, which one can only assume will result in a lot of confusion in the future.
He awakens at the Moonpool with Puddleshine, who brings him to where the rest of his patrol and ShadowClan are waiting. Dovewing tells him she's joining ShadowClan to be with him, as they'd previously discussed. Tigerstar gives a short speech to his Clanmates and they cheer his new name. Tawnypelt tells him that he's missed a lot and that the days have been dark since he's left – with darker days to come. He assures her that they're ready to face them.
In the manga at the end, one day after Darktail's rogues fought RiverClan, Berryheart barely survives Darktail's attempt to drown her. She tells a Clanmate where she's heading, and waits for her mate and kit. Eventually her mate Sparrowtail joins her and explains that their daughter Needletail's being held prisoner with no way to get her out; they'll be killed if they try. The two head out into Clanless territory. Toward the end of greenleaf, Berryheart's brother and sister, Cloverfoot and Sparrowtail, find them. They talk about the mistakes they've made and decide to trust in StarClan to guide them home.
Tropes appearing in this book:
- Abdicate the Throne: Subverted. Rowanstar offers, after seeing Tigerheart handle a Clan dispute better than he would have, to step down to allow Tigerheart to become Clan leader, but Tigerheart refuses.
- Accidental Passenger: Tigerheart hides from some Twolegs in a pile of luggage. Turns out the luggage is on a cart, which gets loaded onto a nearby train, trapping Tigerheart along for the ride. Thankfully, it brings him to the city his mate has fled to.
- A Day in the Limelight: Tigerheart's only POV.
- Dead Guy Junior: Spirekit is named after Spire/Spiresight.
- A Dog Named "Cat": Some of the city cats are named after animals: Ant and Tuna.
- Dream Intro: The prologue is of Spire dreaming about the Clan cats.
- Good Samaritan: The guardian cats are essentially this; they take in injured and weak cats from the city and care for them, not asking for anything in return. Tigerheart and Dovewing stay with them for moons and help them out with some of their problems.
- Love Across Battlelines: Dovewing and Tigerheart'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.
- Meaningful Name: Shadowkit is named in honor of ShadowClan, and Spirekit is named after Spiresight.
- My Secret Pregnancy: Dovewing hides her pregnancy from her Clan, since the father is from another Clan.
- Railroad Tracks of Doom: In this book, trains make their first appearance in the series. Tigerheart and his family are staying close to the tracks to find their way home, when one day the kits are playing on the tracks and an unusually fast train comes. Spire saves Lightkit by dragging her out of the way just in time, and warns Tigerheart that they need to leave the tracks or death will come - "Death too quickly. Death without meaning."
- Secret Relationship: Dovewing/Tigerheart.
- Series Continuity Error: Beetlewhisker of RiverClan appears in the Allegiances, despite having been killed in The Last Hope.
- Rippletail appears as one of the ShadowClan cats the patrol runs into on the way back to the Clans. In the main series, Slatefur was with Sparrowtail, Berryheart and Cloverfoot and rejoined ShadowClan, while Rippletail became a kittypet, and never rejoined the Clans.
