Marco fails to get together with a girl named Marian. Later, Erek King tells Marco the Yeerks' plan to manipulate U.S. satellites to beam Kandrona rays into swimming pools, turning each into a Yeerk pool. That way, Controllers won't have to travel to the Yeerk pool, and the Animorphs would lose their advantage over them. The Yeerks are conducting their latest scheme in the Arctic Circle.

The Animorphs hitch a ride on Visser Three's Blade Ship as flies. On board, they discover cryogenic tubes with strange creatures inside them. Their presence is discovered by the Yeerks, and they're forced to morph their battle creatures. Jake orders a distraction, and Marco rips open the control panel to open the ship's hatch. Rachel, with all her grizzly bear might, manages to make a single, tiny crack in one of the specimen tubes. A liquid nitrogen-like mist spills out, freezing every living thing it touches. A nasty fight ensues, and the Animorphs bail out.

Falling out into the frozen tundra, the Animorphs find themselves freezing to death. They morph wolves, but they need energy to keep going. At night - since none of them can sleep - Ax tells the chilling tale of the new aliens, the Venber, a species from the Andalite moon Venbea, that was wiped out centuries ago by a race known as "The Five", melting them for computer semiconductors. Not only that, but the Yeerks have cloned them by cross-breeding them with humans, giving them their new humanoid shape. Then they find a polar bear had just killed and partially consumed a seal. The Animorphs eat the remains. Much to their surprise, not even Cassie has any scruples. They also find two seal pups - the pups of the seal they'd just eaten. Regretfully, they acquire the pups and leave them to their fate.

Soon the Animorphs find themselves pursued by the creatures Marco had observed in the tubes. They morph seals to escape them, but are attacked by orcas in the freezing depths.

Later, they come across Derek, a young, jocular Inuit, and his "buddy", Nanook the polar bear. Derek tells them about the people with the satellite dish, and how they're even worse than the American hunters who shoot wildlife from helicopters for the adrenaline rush. The Animorphs are presented with an opportunity to acquire the DNA of a native animal, and so they attack Nanook. After pinning him down, they each acquire him, and morph him.

The Animorphs, in their new polar bear morphs, advance on the Yeerk base. They encounter the Venber, engaging them in a brutal battle. They lure the remaining Venber into the hangars, where the above-zero conditions cause them to melt. The Animorphs then steal a Yeerk Bug fighter, and Marco immolates the Yeerk base. Soon to be intercepted by the Blade ship, they morph birds and ditch the alien craft over the West Coast, and fly home.

This marks the first occasion where the Chee pose as the Animorphs for their families while they are away on a long-term mission.

Jake -Peregrine falcon, housefly, Siberian tiger, wolf, ringed seal, polar bear.

Rachel -Bald eagle, housefly, grizzly bear, wolf, ringed seal, polar bear.

Tobias -Housefly, flea, ringed seal, polar bear.

Cassie -Osprey, housefly, wolf, bottlenose dolphin, ringed seal, polar bear.

Marco -Osprey, housefly, gorilla, wolf, bottlenose dolphin, ringed seal, polar bear .

Ax -Northern harrier, housefly, flea, ringed seal, polar bear.