Suddenly alone in a war-torn London, pampered Bertie is cold, alone and scared. With help from his new friends in the community, both those on two legs and on four, he has to learn the way of a stray dog on the streets.

But Bertie doesn't expect the Blitz and the horror it brings, and when his second chance of happiness is threatened, he knows he needs to do what he can to protect it, no matter what dangers lie in his path. Can this extraordinary dog help the ones he loves before it's too late?