Late one night in London, Simon Templar, a debonair private detective known as "The Saint," receives a phone call from a stranger offering him a million pounds in gold. When the man appears on Simon's doorstep, he is stabbed by an unseen assailant, but before dying, the man gasps, "The Tiger, Baycombe and the gold." Simon then calls Inspector Teal of Scotland Yard, a friendly rival, and the dead man is eventually identified as Joe Gallo, a well-known bookie. After Teal reveals that Gallo was involved in a recent bank robbery, Simon suspects that the still-missing loot is the gold that Gallo mentioned, and that he will find the answers in Baycombe. The next morning, Simon and his valet Horace travel to the Cornish village of Baycombe, where they begin searching for "The Tiger," the mysterious leader of the gang of bank robbers. As he meets the townspeople, Simon becomes acquainted with pretty Pat Holmes, who invites him to tea, where he meets banker Lionel Bentley and entrepreneur Bittle. Simon is immediately suspicious of the pair, and as Simon deduces, Bentley and Bittle are in league with The Tiger, who, under the name Tidmarsh, is working in Baycombe as a newspaper reporter. Also present at Pat's gathering is Teal, who poses as a geologist named Professor Kahn. Later, at Simon's rented cottage, one of Bentley's henchmen attempts to shoot him but misses, leading Teal to comment that Simon revealed too much earlier when he intimated to Bentley and Bittle that he knows about their compliticy in the robbery and Gallo's death. Simon insists that the assassination attempt proves that he is on the right track, and then refuses Teal's offer to work together. Soon after, Simon goes to Bentley's home and interrupts as Bentley buys Pat's shares in a defunct gold mine. Simon announces that the banker must have a criminal reason to be buying the worthless mine, and the angry Bentley orders two henchmen to pursue Simon and Pat after they resist his attempts to detain them. Simon sends Pat to his cottage, then returns to Bentley's house, where he discovers a secret passageway to Bentley's office. There, he is captured by Bentley, Bittle and other members of the gang, and accuses them of plotting to plant the stolen gold in the old mine and thereby be able to sell the gold legally. Simon also accuses them of killing Gallo to prevent him from revealing the scheme. Simon throws a knife at Bittle's hand when the criminal tries to shoot him, then is released by Bentley when Tidmarsh telephones and orders them not to kill Simon, but instead get him "out of the way" until they can escape with the gold. Bittle then attempts to get Simon arrested for assault, but the smooth-talking detective pressures Teal into providing an alibi for him. The next day, having learned from Pat that a network of ancient smugglers' caves exists in Baycombe, and that they can be accessed through the local museum, Simon questions Merridew, the curator. Merridew admits his involvement with the gang, but before he can reveal the entrance to the caves, he is killed by a knife thrown by Eddie, one of Bentley's men. Unaware that Eddie has escaped through the secret entrance, Teal, who is in the museum's outer room, arrests Simon for murdering Merridew. Tidmarsh arrives as Teal states that he is taking Simon back to London, and after they leave, calls Bentley with the news that Simon will be off the case. Tidmarsh then orders Bentley to load the gold into a boat anchored near the secret caves, but Bentley, angered by Tidmarsh's arrogance, plots with Bittle to double-cross him. The still unsuspecting Pat then informs Tidmarsh of her plan to sneak aboard Bentley's boat with Horace and retrieve the gold. That night, Bentley and Bittle knock Tidmarsh unconscious before he can join Pat and Horace, who board the boat and begin their search for the loot and the Tiger. Meanwhile, Teal explains to Simon that he arrested him as a ruse to lure the Tiger into a false sense of security, and the pair return to the museum. There, they find the entrance to the smugglers' caves, and Simon sneaks onto the boat. Pat, Horace and Simon eventually find one another, but they are captured by Bentley and Bittle. Tidmarsh arrives onboard soon after, and tells Simon that because he is a worthy opponent, he and his friends can go free. Tidmarsh is determined to kill his double-crossing partners, but Bittle shoots him while he is talking to Simon. Simon then throws a knife at Bittle's hand and succeeds in disarming him. Teal arrives with reinforcements and is informed of Tidmarsh's identity and death, although Simon announces that the police cannot have the gold, as he will be turning it over to the bank's insurance company for a hefty commission. Pat then bestows congratulatory kisses on both Simon and Horace.