The film follows Tom Merriam (Russell Wade), a young officer aboard the merchant ship, Altair, where several mysterious deaths occur. Merriam comes to believe that the ship's mentally unbalanced captain, Will Stone (Richard Dix), might be behind the deaths. The ship's crew, however, blames the death on supernatural events and believes the vessel to be haunted and cursed.
- Affectionate Nickname: Erudite radioman Sparks calls Third Officer Merriam "Tertius," which means "third" in Latin.
- Book Ends: The film begins and ends with Merriam encountering an observant blind beggar on the docks.
- Cassandra Truth: When Merriam deduces that the captain is an insane murderer, none of the crew believe him except for Finn (who can't convey this because he's mute and illiterate). It takes the captain sending a message claiming that Merriam never made it aboard the ship for Sparks (and later the others) to realize that the captain is preparing to kill Merriam and might be dangerous after all.
- Meaningful Echo: After Louie delivers a complaint from the crew to Captain Stone, the captain promises to consider it, but light-heartedly says, "You know, there are some captains who might hold this against you." The next scene features Louie being murdered. Merriam (who was present when Louie talked to the captain) is understandably freaked out when Stone says the exact same thing to him after Merriam has him brought before a board of inquiry.
- Never My Fault: Merriam warns Captain Stone about the need to fix a dangerous piece of equipment and is twice ignored. After it breaks, Stone refuses to take responsibility and chides Merriam for wanting him to exert his authority in a way that would show that he had made a mistake.
- Non-Protagonist Resolver: Finn is a mute crewman who narrates a few scenes but has a small enough role that he isn't listed in the opening credits. In the end, he, rather than Mr. Merriam, is the one who gets the crew to realize that their captain is a murderous nut job. He later walks in on the captain about to murder a helplesss Merriam and kills him after a fight.
- Sherlock Scan: While he's neither a detective nor the main character, the blind beggar in the opening scene deduces that Merriam is a sailor on his first voyage due to how he talks about needing luck. He also deduces that Merriam is an officer and not a seaman after hearing him put down a suitcase rather than a duffel bag.
- What Did I Do Last Night?: Captain Stone's conversation with his girlfriend before departing from a port implies that many of his murderous actions occur during blackouts where he doesn't know what is going on.