Sherlock Holmes in Washington

Pettibone was a British secret agent carrying a vital secret document that had been converted into microfilm. Enemy spies needed to obtain this microfilm to leak crucial information, so they murdered him to take possession of it. The assassins also delivered his body to Holmes as a decoy to throw off the investigation.

The film opens with Pettibone's murder, establishing the high stakes of the espionage case.

Holmes used his deductive reasoning to determine that Pettibone had converted the secret document into microfilm to protect it during transport. He deduced the microfilm was hidden inside a small matchbook with a prominent 'V for Victory' symbol, which Pettibone had been carrying. Holmes realized the microfilm was so well hidden that the person carrying it might not even know of its presence.

Early in the film, Holmes examines Pettibone's belongings and focuses on the matchbook as the key piece of evidence.

Nancy Partridge unknowingly received the matchbook containing the microfilm during a party. The matchbook passed through her hands when guests shared cigarettes at the gathering. Heinrich Hinkel, the chief spy, learned that Nancy had handled the matchbook and kidnapped her to force her to reveal its location or to search her belongings for the microfilm.

During the party scene, the matchbook is passed among several guests, including Nancy, setting up her involvement.

Heinrich Hinkel is the main villain and chief spy operating under the alias Richard Stanley, a seemingly respectable antiquarian shop owner. He orchestrates the entire operation to steal the microfilm for enemy forces. Hinkel orders the kidnapping of Nancy Partridge, confronts Holmes at his shop, and attempts multiple times to seize the microfilm before being captured.

Hinkel appears as the helpful shop owner 'Richard Stanley' when Holmes first investigates, masking his true identity.

Holmes devised a clever trap by tricking Hinkel into believing the microfilm was hidden inside a stamp on a letter possessed by Senator Henry Babcock. Holmes arrived at the senator's office first and secretly revealed the microfilm's true location inside the matchbook. This ruse forced Hinkel to expose himself by attempting to steal the letter, allowing Holmes to apprehend him.

Earlier, Holmes mentions learning from Hinkel that the microfilm might be in a letter possessed by the senator.

After Hinkel was captured, Holmes retrieved the matchbook containing the microfilm. To prevent further espionage attempts, Holmes set fire to the senator's letter, revealing that the microfilm had been hidden inside the matchbook all along, hidden in plain sight throughout the entire investigation.

Holmes had repeatedly hinted that the microfilm was in the matchbook and that the current holder might not realize its importance.

The British government summoned Holmes to Washington because the microfilm contained vital secrets threatening national security, and the murder of the British agent had occurred on American soil. Holmes was needed to track down the spies and recover the microfilm before it fell into enemy hands.

The film establishes early on that the spies have been harassing Pettibone's contacts, delaying their ability to locate the microfilm.

The matchbook with the 'V for Victory' symbol served as the perfect hiding spot for the microfilm because it blended in with wartime morale messaging. Pettibone chose this matchbook specifically because its patriotic design would not attract suspicion, making it an ideal container for top-secret microfilm during WWII.

Holmes immediately notes the matchbook's distinctive design as the key to solving the case.

Dr. Watson had arranged a police rescue plan when Holmes went to confront Hinkel at the antiques shop. When Holmes and Nancy Partridge were taken prisoner and faced imminent murder, Watson summoned the police, who raided the shop. A gunfight ensued, allowing Holmes and Nancy to be rescued, though Hinkel escaped temporarily with the matchbook.

Watson leaves the confrontation scene to organize the backup, setting up the timely raid.

During the police raid at the antiques shop, Hinkel managed to grab the matchbook and escape while the chaos of the gunfight distracted everyone. He used the confusion to flee with the microfilm, forcing Holmes to devise another trap at Senator Babcock's office to recover it.

Holmes had warned that Hinkel was a dangerous opponent who would not give up easily.