Henry A. Perkins, a mild mannered C.P.A, accidently picks up the wrong briefcase - one full of money. Henry assumes it is illicit cash and he decides to keep it. Knowing that the former owner must have his briefcase, he rushes home to book one-way fares for he and his frantic wife out of the country; but she's planning a quiet birthday dinner with their best friends. Add to this confusion, two hard working detectives from rival precincts and a threatening criminal and you have typical Ray Cooney hilarity and non-stop frantic action.