Retired businessman F.G. Lawrence favors Philip Preston for a son-in-law; Mrs. Lawrence prefers Reggie, the Dainty Dude. There's trouble, right there. Mrs. L. becomes suspicious of a stout stranger prowling about the place and tells Mary, the husky cook, to point him out to Serena Slim, the slender sleuth. The mysterious fat man happens to be Mary's beau, so she sics Serena onto John Bouncer, Philip's fat uncle. Serena is some "shadow" and the police must be called in to stop the comedy of error...