The radio talk show host, named Samantha, is a popular personality known for her advice on love and relationships. However, when a mysterious caller named "Mr. X" begins calling into her show, expressing an obsessive interest in her, Samantha's life takes a dark turn.
At first, Samantha ignores Mr. X's advances, thinking it is harmless infatuation from a fan. But as his calls become more frequent and increasingly threatening, Samantha starts to fear for her safety.
Things escalate when Samantha begins receiving gifts and letters from Mr. X, and soon after, people close to Samantha start getting hurt. As the police try to track down the stalker, Samantha turns to her ex-boyfriend, a detective, for help in uncovering the culprit.
As the investigation proceeds, Samantha realizes that Mr. X has been gathering information about her for a long time, and that he knows things about her past that she thought were hidden. With her life on the line, Samantha must find a way to outsmart Mr. X and put an end to his deadly obsession before it's too late.