Sherlock Holmes in Washington

Alfred Pettibone, a British secret agent, is murdered while en route to deliver a vital secret document in the U.S. His body is delivery to Holmes by spies to mislead him. The agents' goal was to protect the microfilm containing crucial information. Holmes begins his investigation into Pettibone's death and the secret document.

Holmes deduces that Pettibone converted the vital document into microfilm to keep it safe. This microfilm was hidden inside a matchbook with a 'V for Victory' symbol. Holmes understands the significance of the microfilm and its role in the espionage plot.

Holmes, avoiding assassination attempts, rushes to Washington, D.C., with Dr. Watson to retrieve the microfilm. They believe that the spies have not yet obtained the microfilm since Pettibone's contacts have been harassed. Holmes aims to recover the microfilm before it falls into enemy hands.

Before his death, Pettibone managed to pass the microfilm hidden inside the matchbook to Nancy Partridge, a debutante and bride-to-be. The microfilm unknowingly changes hands at a party when the matches are passed among guests, eventually reaching the spy Heinrich Hinkel. Nancy is kidnapped by Hinkel's agents.

Holmes locates Hinkel's operation to an antiques shop where he confronts the spy. During a tense exchange, Holmes hints that the microfilm is in the matchbook and is being unwittingly carried by someone who doesn't realize its importance. Holmes is eventually captured during this encounter.

Holmes and Nancy Partridge are taken prisoner by Hinkel's agents during their confrontation. As they face imminent murder, a police raid organized by Watson, who had arranged the rescue, breaks in, leading to a gunfight. The police rescue Holmes and Nancy, but Hinkel manages to escape with the matchbook.

Holmes leads Hinkel to Senator Henry Babcock's office, tricking him into believing that the microfilm is hidden inside a stamp on a letter possessed by the senator. Holmes arrives first and secretly reveals the microfilm's true location inside the matchbook, hoping to trap Hinkel.

Hinkel, armed and eavesdropping, attempts to take the letter that supposedly contains the microfilm. Holmes reveals the significance of the matchbook and the microfilm, attempting to thwart Hinkel’s plan. A confrontation ensues as Hinkel tries to seize the letter.

The police apprehend Hinkel after a tense standoff, preventing him from stealing the microfilm. Holmes then retrieves the matchbook, which contains the vital microfilm, and sets fire to the letter to prevent further espionage. The microfilm's safe recovery concludes the chase.

Holmes reveals that the microfilm was hidden all along inside the matchbook, hidden in plain sight. The microfilm contains vital secrets, and Holmes secures it to prevent further espionage attempts. The story ends with the microfilm protected and the espionage threat neutralized.