When Psychologist Julie West arrives at Cartledge Inn in response to an urgent call from Stefan Lauber, a supposedly reformed criminal recently released from prison, a near-hysterical desk clerk tells her that Lauber has been murdered in his room—room 623.

According to the clerk, everybody keeps asking for that room. The police have already examined the scene, but others have broken in and ransacked the place. Still others want to book a reservation for this particular room number.

Pastor James Burton, whom Julie West secretly loves, teams with her to solve the mystery of room 623. In the proves, they encounter another murder, meet a strange detective, and learn about missing diamonds.