When 12-year-old Zan finds a helpless newborn pup abandoned in an alley, he takes matters into his own hands. His parents won't let him have a dog, so, swearing his sister Kibby to secrecy, he hides the pup - whom he names Smoke - in his bedroom and smuggles food to him. Through quick thinking, and despite a few near-disasters, Zan and Kibby keep their parents from discovering their pet - until Smoke grows too big to hide.

When Zan's parents find out he's been keeping a wolf in the house, they are furious and - terrified. Afraid of what they might do to Smoke, Zan runs away with his beloved companion, and the search is on.

As Zan has protected Smoke, so the wolf becomes Zan's protector in their life among the homeless on the streets of London. But as Smoke nears adulthood, and the authorities close in on the wolf and the boy, Zan is faced with a choice that may mean losing his friend.