The Girl Who Knew Too Much is a 1969 motion picture starring Adam West as Johnny Cain, a nightclub owner and former freelance adventurer who is forced out of retirement when a crime syndicate boss is murdered in his nightclub and investigations lead into unexpected areas.

Tagline: "You have to be crazy or in love — to take on the syndicate!"

The film co-stars Nancy Kwan, Nehemiaf Persoff , Robert Alda, Patricia Smith , David Brian , and noted jazz musician Buddy Greco as nightclub entertainer "Lucky".

The film was a vehicle for Adam West to escape his Batman stereotype by playing a cynical, hard-edged tough guy. Sample dialogue:

Mrs. Smith: "And what do you do for a living, Mr. Cain?"

Cain: "I kill people, Mrs. Smith."

The film was not much of a box office success in theatrical release, but became a staple of late-night showings on WCBS-TV and other television stations in the early 1970s. Despite this exposure, it has never been released on VHS or DVD, and thus is in danger of eventually becoming a lost film.