The dogs of Easthill are having doubts. Some believe in goodness, beauty and truth and that it finds meaning in their lives through a mysterious object called the Thumbald. Others just want to groom their bottoms.

A Border-Collie called Cloud believes more than most. He was found abandoned as a puppy, drifting down a stream on a makeshift raft. With no family to speak of and few other attachments, he finds that he wants to believe in the meaning and mystery of Easthill's sacred prize.

But when a strange black dog upstages an annual festival, the dogs' doubts become a full-blown crisis. Was there ever such a thing as the Thumbald? Or was it always nonsense?

So Cloud decides to go on a journey looking for answers. On the way he meets three companions. Hoo Hoo is a cocky Springer Spaniel with the power to shape-shift (frequently into unhelpful things, like an exploding mushroom). Porker is a greedy St Bernard who can't keep his paws off sausage sandwiches. And Mouse is a shy Dachshund with a disconcerting tendency to disappear at will.

Between them they must work out what's true and what's just a lot of hairy dewlaps ...