 Who knew that an adorable little Welsh terrier could have such dangerous ties? When William "Bill" Denny (Farley Granger) is followed home by a little dog one day, he is totally oblivious to the danger and mayhem he has let himself in for. The dog is oddly the wanted by the mob, who are in turn wanted by the police. Add a skeptical but interfering mother-in-law, and you have plot in which poor Bill fumbling around in, trying, comically, to figure out what is going on, while getting the dog to "Behave Yourself."