In response to a telegram, New York private detective Tippecanoe "Tip" O'Neil travels to see Paul Harding, an old friend and employer, at his Lakeside estate. Although Paul, a gun enthusiast, protests that he did not send the telegram, he confides in Tip that his dog was shot and that someone has sent him letters demanding $200,000. After concluding that the dog killer had used one of Paul's rifles, Tip questions Amy Hutchins, Paul's attractive, gun-toting secretary, who confesses that she sent the telegram. That night, after Tip observes Paul's brother-in-law, Jim Glenray, slip out of the house, Corinne, Paul's ward, is kidnapped by two thugs. Paul insists that Tip, who enjoys a reputation as a tough, "no-holds-barred" detective, handle the kidnapping, but when the son of William, the black chauffeur, is found dead near the estate, Inspector Brock drops by for questioning. The next morning, the kidnappers contact Paul and demand a ransom of $200,000. While Paul delivers the money, "Red" Cable, a bodyguard whom Paul had hired to watch his daughter Nancy, finds thug Maratti on the grounds. With Amy behind the wheel, Red and Tip push Maratti into a car at gunpoint and force him to admit that he was after Jim because he was having an affair with his sister Cleo. After Paul returns from his rendezvous without Corinne, however, Gene Leland, her anxious fiancé, informs Tip that another gangster, Tony Spivali, once had contacted Paul. Armed with this clue, Tip finds Tony at his gambling house and demands information. When Tony refuses to divulge his secret for less than $5,000, Tip seeks the help of Luigi Tersiniani, a Mafia godfather, who intimidates Tony into revealing that Jim had gambling debts with him and was using William, his chauffeur, as a go-between. Tony then states that William had approached him with a proposition involving two hired thugs. Before Tip is able to extract a confession out of William, however, the chauffeur is shot in Harding's study with Amy's gun. Now a suspect, Amy takes Tip to her apartment, where she is attacked by an unseen assailant. After knocking out an over-zealous Gene, Tip then delivers an additional $50,000 to the thugs, unaware that Corinne is an accomplice in her own kidnapping. Corinne, who is then double-crossed by her co-conspirators, returns home and is observed by Tip in an intimate embrace with Paul. When Tony then identifies Paul, not Jim, as the gambler, Tip deduces that Paul and Corinne planned the kidnapping in order to get $200,000, which Nancy had donated from her trust fund. Tip also learns that the thugs accidentally killed William's son, that Paul killed William, and that Paul had attacked Amy because she had a carbon of a list of phony currency serial numbers that Paul had given the police. Thus cornered, Paul attempts to escape with Corinne, but crashes in his automobile and dies.