[citation needed] Two young Irish shapeshifters (or Switchers) face the menace of an encroaching Ice Age caused by monstrous creatures in the Arctic.

Having recently moved to Dublin, Tess finds solitude in her power to Switch (shapeshift), escaping city life in favour of the animal world.

However, she is troubled by a boy named Kevin, who constantly follows her home when she gets off the school bus, and claims to need her help.

After much prodding, Tess agrees to follow Kevin to a house owned by an elderly former Switcher named Lizzie, who reveals that enormous, ice-dwelling Arctic slugs called krools have been roused from a millennia-long slumber by recent oil drilling in the area of their hibernation.

Now that they are wakeful, they have begun to lower the temperature of the Earth so as to make it more comfortable for themselves, and will not stop until they have brought the entire planet into a new Ice Age.

The creatures evade these attacks, and begin to move about the Arctic, killing all the krools they can find, thus causing the snowstorms all over the world to die down.

Her friend made an immense leap of faith as he was swept up in the explosion, allowing him to survive because phoenixes by nature rise from their own ashes when killed.