Charlie Chan in Honolulu

Detective Chan rushes to the hospital to be with his daughter as she prepares to give birth to his first grandchild. The moment sets a personal stake that contrasts with the looming shipboard mystery. This scene establishes the emotional core before the murder investigation unfolds.

Jimmy intercepts a message intended for Charlie about a murder on board the freighter Susan B. Jennings. He decides to test his skills by stepping into the investigation aboard the ship. His actions pull the Chan family into a dangerous puzzle.

Jimmy and his younger brother Tommy board the freighter Jennings pretending to be Charlie Chan, hoping to solve the case from within. They slip aboard during the voyage toward Honolulu. The ruse is short-lived, and the real Chan soon arrives to take charge.

The real Chan reaches the ship and begins questioning the motley crew, heiresses and passengers alike. He quickly narrows the pool of suspects and establishes a methodical approach. Tension rises as the mystery deepens aboard the crowded freighter.

Chan interrogates a motley assortment of crooks, heiresses, and crew while the only witness remains Judy Haynes, the ship's secretary. Judy's testimony becomes crucial as alibis start to crumble under scrutiny. The atmosphere thickens with secrets under a ticking clock.

A suitcase containing $300,000 disappears, a key element in a tug-of-war divorce settlement between Mrs. Carol Wayne and the murder victim. The missing money becomes a focal point as Chan connects it to the motive behind the crime. Greed and betrayal on the ship intensify the investigation.

Carol Wayne is found strangled to death in Judy Haynes' cabin, following a heated argument between the dead woman and Dr. Cardigan. The discovery widens the suspect list and ties the medical eccentric to the crime. Chan's deductions hinge on the cabin’s grim clue.

Johnny McCoy and Detective Joe Arnold are presented as would-be extraditions, but Chan exposes them as fellow criminals trying to sneak back into the USA. Their misdirection collapses under Chan's scrutiny. The revelation tightens the net around the true killer.

Jimmy starts a controlled fire on the ship to panic the killer into grabbing the hidden money and making a run for it. The tactic is reckless, but it serves to flush the culprit from the shadows. Chan remains focused, using the chaos to piece together final clues.

The handgun used in the murder ends up in Deckhand Al Hogan's hands, only to be returned to Chan. The weapon becomes a pivotal piece in validating the chain of evidence. The confrontation turns toward the killer as the gun’s custody is clarified.

Lights go out and the gun disappears during the blackout, but an infrared camera reveals the killer's guilt beyond all doubt. Chan leverages this unseen evidence to publicly name the murderer. The infrared breakthrough makes the final accusation undeniable.

With the murderer exposed, the remaining passengers await justice as the ship heads toward shore. The clues—money, motive, and misdirection—align under Chan's methodical deduction. The case reaches its close as order is restored aboard the vessel.

The voyage ends with Charlie Chan's first grandchild's cries, as passengers gather around the ship-to-shore phone listening to the newborn's sounds. The scene offers a warm counterpoint to the earlier violence. Personal joy ties the day together with the procedural mystery resolved.