Travelling alone on a luxury liner, Regina Clausen disembarked in Hong Kong saying she would rejoin the ship when it docked in Japan. She was never seen again ... Three years later, psychologist Susan Chandler does a series about vanishing women on her radio talk show. When a caller, who refuses to identify herself, tells of meeting a man on a cruise who gave her a ring inscribed You Belong to Me, but who then disappeared when she refused to leave the ship with him, Susan thinks little of it.
But then Regina's mother appears at Susan's office with a ring bearing the same inscription, which was found amongst her daughter's belongings. Susan begins to suspect that they are on the trail of something dangerously sinister... Setting out to do some investigating of her own, Susan finds herself confronted with the horrifying possibility that she might actually know the killer. Suddenly she is in a race against time, realizing almost too late that the hunter has become the hunted, and Susan herself is marked for murder.