The Saint Steps In is a mystery novel by Leslie Charteris, first published in 1942 in the United States by Doubleday, Doran and Company and in 1943 in the United Kingdom by Hodder & Stoughton. It is the twenty-fourth volume in the long-running series featuring the character Simon Templar, a sophisticated adventurer known as "The Saint."
The novel is set during World War II and involves Simon Templar's intervention in a case of industrial espionage. The plot follows Templar as he protects a young woman and her father, the latter of whom has developed a formula for a new synthetic textile. The narrative focuses on the efforts of various parties to obtain the formula and the security implications of the invention during wartime.
Within the internal chronology of the series, The Saint Steps In followed the short story collection The Saint Goes West (1942) and preceded The Saint on Guard (1944). The work reflects the shift in the series toward wartime themes, a transition that occurred while Charteris was residing in the United States. Like many of Charteris's novels from this period, the book emphasizes Templar's cooperation with official authorities against threats to national interests, a departure from his earlier depictions as a more independent, "Robin Hood"-style outlaw.
