Spear and Fang fight to protect Mira and her people from the Vikings.
This episode features the following tropes:
- Action Mom: Rikka, the Viking chieftain's wife, has two sons and fights fiercely to defend her village, even almost killing Fang at one point. One woman attacking Spear has a baby in a sling.
- All There in the Script: The Viking chieftain's son is named Eldar, according to the credits.
- Asshole Victim: Downplayed but still present. Spear and Fang are driven into such a corner that they snap and slaughter a village full of warriors, women, children and elderly included. Disturbing, but given that the Vikings wantonly slaughter and enslave seemingly peaceful people like Mira (as the chieftain returns, he's bringing another batch of victims), it's hard to feel too sorry for them. Indeed, the level of slaughter only really escalated to that point because the bear-riding party forced Spear and Fang backwards into the village, and then they continued attacking them even when Spear and Fang were clearly trying to leave. It's likely that they are on the receiving end of a level of brutality that they have inflicted on numerous others, and that's without considering some of the other things Vikings were known to do to their victims.
- Badass Bystander: Seemingly the entire population of the Viking village is made up of combatants, men, women, and even children taking up arms against Spear and Fang without hesitation. But this simply drives the two to slaughter the entire population of the village.
- Behemoth Battle: Fang, a Tyrannosaurus Rex, Vs. giant Cave Bears.
- Big Entrance: Fang gets one when she arrives to help Spear. The bears slowly advancing towards him suddenly stop, smell the air and become agitated. This is followed by loud sounds coming from the woods and a large flock of birds flying away, then Fang herself appears on the scene by leaping onto a roof and roaring. Though this is somewhat undercut by her falling through the ceiling, but she more than makes up for it by bursting from the house and attacking the lead Viking.
- Child Soldiers: Rikka's young son take to the rooftops with a bow and shoots at Spear before physically attacking him. Spear notices one of the other Vikings attacking him is just a little girl and is shocked to see one of the women has a baby strapped to her chest as she menaces him with a spear.
- Death of a Child: Spear accidentally kills Rikka's child son trying to throw him off non-fatally when he bashes his head on a rock as he lands. Having been a father once himself, he's horrified, but doesn't have much time to reflect on it before the rest of the village resumes attacking him and Fang. Another child and a woman holding a crying infant are also seen about to attack him in one scene, and, although we don't see them afterwards, we can assume they also died afterwards.
- Death by a Thousand Cuts: The Vikings' main tactic against Fang is to either surround or disable her and lay into her with axes, spears and arrows in the hopes of bringing her down. They also briefly attempt this on Spear by circling him and slashing him repeatedly. Unfortunately for them, all it does is make them mad.
- Don't Make Me Destroy You: This is very much the sentiment Spear and Fang try to communicate to the surviving villagers after Rikka and her youngest are killed in the fight, Spear mounting Fang and the Duo trying to flee the village by the nearest exit, growling threateningly at the vikings as they do so to keep them away and avoid both having to shed more unnecessary blood. Unfortunately, the red mist that descends on the village results in them accidentally heading towards the cliff face when they get disoriented due to the poor visibility, and the viking's stubborn instance on pointlessly aggravating a superior opponent after their best fighters have all been killed results in them eventually getting killed to the last man, which is the only way Spear and Fang have enough breathing room to leave the village.
- Double-Meaning Title: The Red Mist can refer to both the red fog that ends up covering the Viking settlement or the red mist that settles over Spear and Fang after they are repeatedly attacked by Vikings and backed into a corner until they finally reach their Rage Breaking Point and slaughter the entire tribe.
- Even Evil Has Loved Ones: The Vikings may be merciless raiders and slavers, but they love their families as much as anyone else. When Rikka's husband and eldest son Eldar return to find their family and village slaughtered, they're devastated and take the time to give them proper funerals before setting off to avenge them.
- "Everybody Dies" Ending: Spear and Fang end up slaughtering every last member of the village in their rescue of Mira, though it's portrayed as something they're driven to do after the bear-riding party winds up forcing them backwards into the village when they're trying to escort the slaves out, and every single villager they face keeps attacking them to avenge those who were killed, even as doing so only results in more deaths. At one point, Spear and Fang clearly try to leave the village but end up heading towards a cliff edge in the mist, and then get pelted with arrows and projectile attacks until they snap with rage and just kill everybody to make it stop.
- Immediate Sequel: The episode picks up right where "Dawn of Man" left off with Spear preparing to face the Vikings on their bears.
- Last of Their Kind: The Viking chief and his son at the end of the episode, who are Genocide Survivors on account of having been away collecting slaves when Spear and Fang attacked the vikings to free Mira and they return to discover the ruins of their village and that they are the last surviving members of their people.
- Manly Tears: The Chieftain and Eldar quietly weep over the loss of Rikka and her younger child.
- Maybe Magic, Maybe Mundane: The red mist that blankets the village could be a natural phenomenon, given the foggy atmosphere as the hunting party return, but thanks to the increase in the poor visibility of the surroundings, Spear and Fang get lost when trying to leave the village and wind up cornering themselves by a cliff face, and when the Viking's stubborn insistence on attacking them regardless pushes them to their Rage Breaking Point, the same mist proves excellent cover for the superior fighters to ambush and tear through their enemies with ease, negating the viking's advantage in numbers against them, implying that there is an element of divine retribution present for the Viking's absolute slaughter at the duo's hands.
- Mook Horror Show: After Spear and Fang are unable to escape the village, the repeated attacks eventually cause the two of them to go into a rage and they begin slaughtering them from the cover of the mist. Fang's silhouette in particular looks downright demonic as she tears her way through the villagers.
- My God, What Have I Done?: Spear has this reaction when he inadvertently kills Rikka's younger son. Mira has a minor one after beheading a Viking, but she gets over it quickly. Notably, they're the only ones shown to have this, as none of the Vikings are portrayed having any regrets about their slavery, nor trying to keep attacking Spear and Fang to avenge their fallen, even as doing so only makes the body count rise.
- Off with His Head!: Quite a few Vikings lose their heads to Spear and Fang—Mira ends up decapitating one with his own axe.
- Pet the Dog: The Chieftain and Eldar free the slaves they've captured after finding their family and village massacred. Possibly more because the slaves would prove burdensome in their now singular quest for vengeance than for entirely altruistic reasons, but they still get points for not offing them on the spot.
- Red Is Violent: The eponymous red mist descends on the village just when Spear and Fang stop merely defending themselves and the slaves from the vikings and give in to their rage, slaughtering the tribe.
- Revenge: With their clan entirely destroyed, the Chief and Eldar are left with nothing but only one thing on their mind: vengeance against the man and the dinosaur that did this to them.
- Rule of Symbolism: The nature of the red mist goes unexplained, but it's an effective visual metaphor for the rage that descends on Spear and Fang.
- Say My Name: The Chieftain screams his wife's name in raw anguish while cradling her in his arms upon realizing that she's dead.
- Scare the Dog: As the Vikings slowly close in on Spear preparing for a fight, their mounted bears suddenly stop and start sniffing the area, becoming increasingly agitated. Then a large flock of birds leave the forest. Fang is coming and they know it.
- Scarily Competent Tracker: The Chieftain is able to deduce Fang, Spear and Mira's escape route from the village from the bloodstains they all left on the stairs leading down to the docks to steal one of their boats, the visual imagery implying he was able to deduce their numbers and rough species from the blood markings left behind. At the end, he and his son set out to pursue them over water, despite them having fled by boat, with it being implied they're fully confident of finding their quarry no matter how much of a head start they have.
- Shown Their Work: The Viking Funeral at the end is correctly portrayed as something reserved solely for notable members of a clan, as only Rikka and her younger son are placed on the ship. The rest of the clan are put in a communal burial akin to a crypt.
- Unstoppable Rage: Spear and Fang are clearly individually superior to the Vikings but are slowly getting pushed back. As things get worse, the pair clearly become angrier and more ruthless until Spear is momentarily snapped out of it when he accidentally kills a child by knocking him into a rock. They try to escape into the titular red mist but trapped between a sheer cliff face and a rain of arrows, they lose themselves in their rage. What follows is a horror show as the Vikings, trying to fight the pair in the shadows, are mercilessly slaughtered. Given Eldar and his father leave alone and burn the village, it's very likely that they killed every person in the village before they left.
- Viking Funeral: One occurs at the end of the episode when Eldar and his father put their family's corpses onto the ship. The Chieftain is reluctant to release the arrow, however, so Eldar does the job for him.
- Would Hit a Girl: Spear has no qualms cutting down the Viking women along with the men.
- Would Hurt a Child: Downplayed. Spear is horrified when he sees young children joining in the adults in menacing him and even seeing a crying child strapped to one woman's chest as she menaces him with a spear. When Rikka's youngest son starts pelting him with arrows he's angered, but shows restraint, choosing to ignore his attacker in favor of the more adult ones as much as he can, and the boy's death comes about from him continuing to attack Spear even close-range in Spear's element, jumping on Spear's back and clawing at his face, causing the caveman to throw him off in pain, and his head to hit a rock on his landing, something which sparks remorse in Spear.
- Your Size May Vary: While an ongoing trend in the show with Fang, it's noteworthy here not only with her being portrayed probably at the largest she's been in the show to this point (in numerous shots she dwarfs a real Tyrannosaurus) but also establishing a trend that would run through season 2: regardless of how she's scaled in other shots, if Fang is fighting humans she will be invariably shown at a huge size.
