A gruesome murder committed aboard a luxury ocean liner forces Dr. Gideon Fell to identify a killer hiding in plain sight among the passengers. Dr. Fell must navigate the confined, high-stakes environment of a ship at sea, where the suspect pool is limited and the social dynamics are rigid. He works to dismantle a series of seemingly impossible clues that defy logical explanation. The narrative employs a traditional third-person perspective, focusing on the methodical collection of evidence and the interrogation of witnesses. The primary opposition stems from the killer's calculated manipulation of the ship's layout and the passengers' conflicting testimonies.

Readers frequently highlight the intricate puzzle construction that defines this work as a classic example of the locked room mystery genre. Discussion often centers on the balance between the lighthearted, often humorous tone of the dialogue and the grim nature of the central crime. Critics note that the pacing relies heavily on the intellectual rigor of Dr. Gideon Fell, whose deductive process serves as the primary engine for the plot. Many fans of the genre appreciate the atmospheric setting of the ocean liner, which effectively isolates the characters and heightens the tension of the investigation. The narrative is widely regarded as a representative piece of the author's ability to craft complex, logical riddles that challenge the reader to solve the crime alongside the detective.