Gentle Ealing comedy about childhood, guilt and half-truths starring a young James Fox (then known by his real name, William Fox) as Johnny Brent, a mischievous boy who tricks a younger boy (Keith Robinson) into giving him his magnet in return for an 'invisible' clock. Having successfully obtained the magnet, Johnny immediately starts to feel guilty about his swindling behaviour. His guilt sparks a chain of misplaced assumptions that lead to a search being mounted for the boy, who has run away after becoming convinced that he is wanted for murder.