After a run of bad luck, ex-police officer turned private investigator Jonny Double finally has a case. Who has it in for Wilson Twain? Mr. Twain was beat up, with a photo of him dead left at the scene. Twain meets Jonny at the Domino Discotheque, where Twain shows Jonny the photo, claiming it is his twin brother, a syndicate man. Twain wants Jonny to get the syndicate off his back, but he can’t go to the police without revealing his brother’s connection to the syndicate.
Jonny goes to visit his old friend, Lt. Branigan of the S.F.P.D., to try to get information on the Syndicate. After Branigan refuses, Jonny heads to the Devil’s End, to try to get info out of a pool hustler named “Fish-Eye,” who also refuses. Leaving the Devil’s End, Jonny is jumped by syndicate thugs, who beat him senseless to convince him to drop the case.
Beat up pretty badly, Jonny goes to the only one he can turn to: Crystal Cross, a waitress at Aunt Maude’s all night diner. Crystal patches Jonny up, and Jonny heads back to Twain to get more leads. Twain’s lead sends Jonny to the offices of Piker and Glass. Jonny sneaks into the offices as a janitor, where he overhears Piker speaking to the thugs earlier. Piker notices Jonny snooping, and they get the drop on him. One of the thugs walks Jonny up to the roof at gunpoint, intent of making his death look like suicide.
Jonny manages to get a good kick in on the thug, and their fight pushes the thug over the edge. Jonny flees, and the syndicate thugs give chase. Jonny leads them to a local haunted house, and uses the distractions of the haunted house to separate and take the thugs down one-at-a-time. Jonny not only gets the money from Twain, but pictures of the fight taken by an automated camera.