The crew of a ship find a sunken submarine — one that has the sound knocking emanating from it. As they explore the submarine, Chief Bell begins to behave oddly, as though he is afraid of something, and starts to see ghosts. Against all odds, it turns out to have been the same submarine Bell served on years ago. He inadvertently knocked the cover off a lamp during a blackout, allowing the Japanese to see and sink the sub. He believes his dead comrades have come back for him.
The Thirty-Fathom Tropes:
- Artistic License History: It is mentioned that the submarine 714 was sunk during the First Battle of the Solomon Sea on August 7, 1942. In reality, the battle took place from August 8 to 9, 1942.
- Chromosome Casting: Given its military theme, this episode has an all-male cast.
- Driven to Suicide: Bell jumps overboard as he believes that the ghosts of his former crew mates blame him for the 714 sinking.
- Ghost Ship: The 714 is seemingly haunted by the ghosts of its crew.
- It's All My Fault: Bell blames himself for the Japanese sinking the sub and killing all his comrades-in-arms.
- Maybe Magic, Maybe Mundane:
- One trip to the submarine reveals that a piece of the ship swinging loose could have been responsible for the banging noises...but it also reveals that one of the dead sailors was holding a hammer.
- Earlier, Doc discovering seaweed in the hallway where Bell claimed to have seen ghosts.
- Modern Major General: Captain Beecham (perhaps unintentionally) comes across as this. Not only does he utterly fail to stop the deranged Bell from running out of the room they were both in, but unlike Doc who desperately races to stop him from jumping overboard, he slowly walks behind them looking more annoyed than anything else.
- Sole Survivor: Bell was the only survivor of the sinking of the 714.
- Survivor Guilt: Bell feels that he should have died along with his crewmates, and he thinks they agree with him.