The Corn Mill Cats are two cats called Half Ear and One Side Whisker who live in a corn mill. They are always busy frightening away the mice that live in the mill and stopping them from stealing the corn from the sacks. The Corn Mill Cats have a friend called Chobler who lives in a nearby restaurant. Chobler is a large, overweight tabby cat who eats far too many of the leftovers from the restaurant kitchen. He is a jolly cat who sometimes shares his pickings with the Corn Mill Cats.
This story tells of another adventure of the Corn Mill Cats – Half Ear and One Side Whisker – together with their friend from the restaurant, Chobler.

When they are persuaded by Sway Leg Jim, a cat that lives on a barge, to take a trip with him on the canal, it is not long before the Corn Mill Cats realise that living on a barge can be a little more hazardous than they had imagined.