After attorney Frank Girard is murdered, Detective Al Church suspects that Ms. Leigh Cullen is the perpetrator, as she was supposedly last seen with the man. However, after Leigh's alleged twin sister, Tracy, shows up at the police line-up with Leigh, Church is left puzzled and with no specific suspect to pinpoint. Therefore, Church asks Psychiatrist Dr. Jim Eiseley, an acquaintance of Leigh's, to evaluate the sisters and run tests on them in hopes of filtering out the murderer. However, Eiseley's increasing involvement with Leigh complicates things with Tracy in the picture.

Mandrake, a famous magician, and his assistant, Lothar, come to the aid of an amusement-park owner who is being blackmailed by a madman who is killing the park's customers until he gets his money.

A brilliant attorney gets rid of her boring husband by faking his kidnapping and keeping the ransom. The FBI may be fooled, but not Columbo.