Alf Gorilla is minder to Batty and his gang of rats. They live on a rusty tug on the River Thames, but their old enemy, Oily Sludge the wharf cat, has plans to cut them adrift. Meanwhile, the zoo director organises the biggest search ever for his escaped gorilla, inviting all the children of London to join in. Alf causes chaos in the hide-and-seek which develops.

The witty illustrations by the author accompany this action-packed story. Both brim over with humour.