The film stars Frank Sinatra, Raquel Welch, Dan Blocker, Richard Conte, Martin Gabel, Lainie Kazan, and Pat Henry.

While diving off the Miami coast seeking one of the 11 fabled Spanish galleons sunk in 1591, private investigator Tony Rome discovers a dead woman, her feet encased in cement (concrete), at the bottom of the ocean.

Rome reports this to Lieutenant Dave Santini and thinks nothing more of the incident, until Waldo Gronsky hires him to find a missing woman, Sondra Lomax.

After investigating the local hotspots and picking up on a few names, Rome soon comes across Kit Forrest, whose party Sondra Lomax was supposed to have attended.

Rome's talking to Forrest raises the ire of racketeer Al Mungar, a supposedly reformed gangster who looks after Kit's interests.

When Rome tracks down Gronski to the seedy massage parlor he owns, Dan Blocker is shown watching a TV which is blaring the Bonanza theme.

Critic Roger Ebert gave faint praise in a generally scathing review by commenting: "In the movie's few good scenes, Sinatra once again painfully reminds us what a controlled, effective actor he is.

"[12] Variety described Sinatra's character as being "on the trail of people in whom there couldn't be less interest", Raquel Welch "adds her limited, but beauteous contribution", and Dan Blocker "is excellent as a sympathetic heavy".