The Saint In Palm Springs

Peter Johnson was killed because he was transporting three valuable stamps worth $200,000 from New York to his niece Elna in Palm Springs. The stamps had been smuggled out of a foreign country, and that country sent agents to recover them by any means necessary. Johnson's murder was intended to steal the stamps, though the killer was unaware that Templar was also protecting the shipment.

Templar's initial assignment by Inspector Farnack explicitly mentions the high value and danger associated with transporting such rare stamps.

The stamps were stolen by a hotel guest who remains unnamed in the main plot resolution, though Margaret Forbes was revealed to be working for the country from which the stamps were smuggled. The stamps were hidden in a pillbox, which Pearly Gates discovered during his search of the guests' belongings. However, Gates could not remember which guest owned the pillbox, complicating the identification.

Templar's decision to have Gates steal from all hotel guests directly leads to discovering the stamps hidden in the pillbox.

Margaret Forbes was revealed to be an agent working for the country from which the stamps were originally smuggled. She was not simply a fellow passenger but an operative sent to recover the stamps. When she held up Johnson at gunpoint to take the stamps, she was attempting to retrieve her country's property, though her actions still constituted theft and murder in the eyes of the law.

Forbes's introduction on the train shows her exchanging cautious banter with Templar, hinting at her deceptive nature.

Templar set a trap by allowing guests who had been robbed to reclaim their property, hoping to identify the thief. The plan backfired when one of the criminals, desperate to prevent the trap from succeeding, killed a police officer during the ensuing chaos. The murder was meant to stop the investigation and allow the criminals to escape with the stamps, but Templar managed to keep the stamps secure despite the violence.

The failed trap directly follows Templar's decision to use the recovered property as bait, which the criminals would naturally try to prevent.

Templar set a trap at Joshua Tree National Park where he confronted a hotel guest he suspected of being the mastermind. Using his cunning, Templar tricked the man into confessing to the murders of Peter Johnson, the policeman, and Margaret Forbes in front of the Police Commissioner and his men. The confession, combined with the mark left by Templar's ring on the killer's face, provided conclusive proof of the criminal's guilt.

Earlier clues included the ring mark on the original attacker and the complex web of crimes that pointed to a coordinated gang operation.

Simon Templar struck the unseen attacker with his ring, which bears his distinctive Saint sign, leaving a physical mark on the killer's face. This mark served as crucial forensic evidence linking the original murderer to the crimes. When the mastermind was exposed, the ring mark on his face provided additional proof of his guilt beyond his confession, strengthening the case against him.

The attack on Peter Johnson was the first moment Templar used his ring against an assailant, and the mark becomes a key piece of evidence later.

When Elna Johnson expressed romantic interest in Templar at the film's end, he responded that while he was tempted, he preferred to play singles rather than doubles. This was a tennis pun, referencing Elna's profession as a tennis pro, singles being a one-on-one match versus doubles which involves two partners. The line reinforce Templar's preference for his independent, solitary lifestyle as a vigilante rather than settling down.

Elna's role as a tennis pro for the hotel is established early, making the pun land naturally in the closing scene.

Margaret Forbes was killed by a rival thief while making her getaway after attempting to steal the stamps from Johnson at gunpoint. Though she was an agent trying to recover her country's property, other criminals in the gang viewed her as competition and eliminated her to prevent her from succeeding or revealing their operation. Her death added to the body count and intensified the mystery.

The presence of multiple competing criminals in the plot set up the dangerous dynamics that led to her demise.

Pearly Gates was a reformed pickpocket whom Templar had previously helped, creating a friendship and debt of loyalty. When Gates was employed by the hotel to provide security, Templar persuaded him to use his pilfering skills to steal from all the other guests in order to identify who had stolen the stamps. Gates's criminal past made him perfect for the task, and his gratitude toward Templar motivated his assistance.

Templar's relationship with Gates is established as a prior connection, showing a pattern of the Saint helping reformed criminals.

The thief hid the stolen stamps inside a pillbox, which was discovered when Pearly Gates searched through the guests' belongings. The specific method of concealment was chosen because a pillbox was small, inconspicuous, and could easily be overlooked during a search. However, Gates could not remember which guest's belongings contained the pillbox, delaying the identification of the actual thief.

The stamps being found in a pillbox connects to the earlier theft at the hotel, where items were taken from all guests.