Ken is employed by the owners of a nursing home to investigate a series of petty thefts of patients' money. Because of pressure of work, he passes the case to Harry who goes to stay at the nursing home, posing as a businessman suffering from stress and a nervous breakdown. Laura also helps, posing as Harry's gushing and utterly spoilt daughter! After eliminating the cleaner and the gardener, Harry soon suspects Mary Foster, an eccentric old lady who is a long-term patient. He marks a wad of 5 notes and leaves them in his bedside drawer. They soon disappear and Harry finds them in Mary's handbag. He presents his findings to the Matron, telling her that he has traced the thief. Much to his surprise, the Matron herself confesses to the thefts. She has been taking the money to give to Mary, in order to perpetuate a white lie - Mary thinks that her son, living in New Zealand, is paying for little treats on her birthday, whereas in fact the son died two years ago and the Matron hasn't the he