The Falcon in San Francisco

Annie claims she's being held prisoner by her nurse Carla Keyes and butler Loomis, but this appears to be a fabricated story. She's a lonely girl who created the kidnapping narrative to get attention from Tom Lawrence, whom she met on the train. Her shifting accusations, first blaming the nurse, then blaming Loomis, suggest she either has emotional issues or is being manipulated by someone else to create confusion around the actual criminal activity.

Earlier on the train, Annie's abrupt interruption when her nurse arrives hints that she fabricates stories to get attention.

Duke Monet is actually De Forrest Marshall, the general manager of Star Coastal Lines and the father of Joan and Annie Marshall. He created the criminal identity of Duke Monet to operate in the underworld while keeping his criminal past hidden from his daughters. He uses this double life to protect them from knowing about his illicit activities, including owning the S.S. Citadel and running a smuggling operation.

The photograph of a ship's officer found in Carla Keyes' room hints at her connection to Monet.

The S.S. Citadel is a cargo ship owned by Duke Monet (De Forrest Marshall) that carries a hidden shipment of raw silk mixed in with legitimate hemp bales. This illicit cargo is the center of the entire criminal scheme. Doreen Temple and Peter Vantine plan to hijack the silk shipment, which is why they interrogate Tom about the ship's schedule and cargo. The ship becomes the final battleground where the confrontation unfolds.

Doreen questions Tom about the S.S. Citadel early in the film, establishing the ship's significance.

Duke Monet (De Forrest Marshall) killed Nurse Carla Keyes. He murdered her because she was one of the people he hired to watch over his daughters, but she became a liability connected to the criminal investigation. When Tom reveals that Monet killed both Carla Keyes and Loomis, it exposes Monet as the mastermind behind the murders, though his motivations were rooted in protecting his criminal operation and his family secret.

The discovery of the ship's officer photograph in Carla's room connects her to Monet's criminal activities.

Loomis was shot dead by an unseen assailant while someone was rummaging through Nurse Carla Keyes's room. The killer is never explicitly identified on-screen, but the circumstances suggest it was Duke Monet (De Forrest Marshall), since Tom later reveals that Monet killed both Carla Keyes and Loomis, the very people he hired to watch over his daughters. Both murders were committed to silence anyone connected to his criminal operations.

The timing of Loomis's death coincides with Tom's investigation into the connections between the Marshall family and the criminal underworld.

Tom agrees to help Monet because the immediate threat from Doreen Temple and her gang is greater. Doreen plans to hijack the silk shipment and kill everyone involved, so Tom works with Monet to stop the hijacking. Additionally, Tom recognizes that Monet's primary motivation is protecting his daughters Joan and Annie, making him a reluctant ally rather than a pure villain. Tom uses the situation to protect the innocent while bringing down the more dangerous criminal elements.

Monet's earlier confession to Joan about his secret identity emphasizes his paternal protective instincts.

Doreen Temple is romantically involved with Duke Monet (De Forrest Marshall). She posts his bail and works with him in the criminal underworld, though she eventually turns against him when he becomes a threat to her own plans. Their relationship is complicated by Monet's secret identity, he uses the name Duke Monet to operate as a criminal while maintaining his respectable public life. Doreen knows his true identity but eventually sides with Vantine in the attempted hijacking, making her an adversary by the final act.

Doreen's early interest in Monet's shipping operations hints at their romantic and criminal connection.

Joan Marshall meets De Forrest Marshall (who she knows as her father, not as Duke Monet) on Telegraph Hill because they are secretly lovers. However, the truth revealed during this meeting is that De Forrest Marshall is actually Duke Monet, and he has been living under a secret identity to protect his daughters from his criminal past. The meeting is actually Joan meeting her father, not a secret lover, but the confusion stems from the fact that she doesn't know his true identity.

Annie's tip about Joan meeting a secret lover directly leads Tom to discover the father-daughter connection.

Goldie Locke serves as Tom Lawrence's loyal sidekick throughout the investigation. He accompanies Tom on the train, helps investigate Annie Marshall's claims, discovers the newspaper revealing Duke Monet's ownership of the S.S. Citadel, and assists in boarding the ship to uncover the hidden silk cargo. While Tom does most of the detective work and confrontation, Goldie provides support and helps uncover crucial evidence that connects the dots.

Goldie's discovery of the newspaper article about the ship's ownership provides the key breakthrough.

Doreen Temple posts bail for Tom Lawrence because she wants to control the investigation and keep him close to the criminal operation. By bailing him out, she positions herself to interrogate Tom about the S.S. Citadel and a man named Peter Vantine. She uses the bail as leverage to force Tom into her apartment for questioning, where her bodyguard Rickey poses as a police officer and warns Tom to stay away from Duke Monet and the ship.

Doreen's promise to reveal her motive later ties her to the criminal conspiracy.