Ken and Harry are guarding Tinkerbell, a greyhound, at Woodcote Park, before her big race. The owner, Mr Hancock, insists that Tinkerbell must be fed ""Mr Marrow"" dog food and a detailed record must be kept of how much of it she eats. Harry gets Rocky to feed and walk the dog, and it soon becomes clear that Tinkerbell hates ""Mr Marrow"". An attractive blonde woman turns up at Woodcote, delivering cases of wine in a Range Rover. While Harry and Rocky are helping to unload the wine, she drives off with Tinkerbell. Harry and Rocky try to trace the owner of the Ranger Rover. Then Rocky has an idea: there is going to be a charity event before the greyhound race - perhaps the dog thieves will be there. They locate the car and follow it back to an opulent house owned by a Mr and Mrs Hipkiss who claim to own Tinkerbell. Mr Hipkiss tells them that Hancock used to work for him but wasn't up to the job. Hipkiss believes that Hancock had stolen Tinkerbell in revenge for (as he sees it) being sacked
