Nothing will stop Shawn from going after the ex-cop who shot his father. Karen Vick gives Shawn the go-ahead to proceed on his own. Chelsea visits Henry in the hospital and since he has a tube down his throat, he has to listen to her.
Shawn is jealous when Juliet is undercover at a dating service trying to meet a man who has killed several women. Gus meets a woman through the service; Shawn thinks she is the killer instead of a man. Madeleine is in town to help Henry.
Shawn & Gus help two college students who are filming a documentary in the forest. They are trying to prove the existence of a big-foot-type creature who is rumored to live there. They find the supposed creature but also some dead bodies.
Shawn & Juliet host a house-warming party. Juliet's parents attend, and it seems the step-father is a boring accountant. As he and Henry meet for lunch, it turns out the father has a few secrets involving gambling, debts and more.
An homage to the movie Clue (1985) (thus the episode title), guest starring three actors from the 1985 movie: Martin Mull, Christopher Lloyd, and Lesley Ann Warren. The episode is dedicated to Madeline Kahn. The show featured viewer-selected endings, voted separately on the East and West Coasts.
Carlton's jailbird girlfriend Marlowe is released from prison and ends up staying with Juliet. Carlton also moves in. Shawn gets a case from a circus performer who asks Shawn to find the missing star act. Gus babysits Maximus at the circus.
Lassiter is getting married, so Shawn, Gus, & the others guys throw him a bachelor party, while Juliet, Karen throw a bachelorette party for Marlowe. In route to the wedding, they encounter a local mob boss. Juliet questions Shawn's psych.
Two versions of a crime are shown. One where Juliet knows Shawn is a fake psychic, he leaves the wedding and finds a girl who was beaten and just barely alive. In the other, Juliet does not know, and a girl has been murdered.
Juliet tells Shawn to move out of the apartment. Shawn moves in with Woody and Juliet gets a new roommate. When a body is found and the investigation started, Shawn thinks the new roommate killed the victim.
At Gus' pharmaceutical job, Creech could be the world's worst boss. As Gus quits that night, he finds Creech dead. Gus ends up getting his fingerprints on every piece of furniture. He goes to Shawn, who also ends up messing the crime scene.
A radio DJ is killed while on the air, and Shawn & Gus help the police with the crime. They determine a fan of the DJ seems to be involved. She says she is being stalked by a person named Bob, and he is the one who might be the killer.
While bird watching with friends, Henry finds a dead body and decides to investigate the case. Shawn & Gus also investigate, but Henry seems to be a step ahead of them. Henry knows the plastic surgeon and it looks like she is guilty.
Sean and others investigate a man who claims he has been poisoned, and his client's safe deposit box contents are in jeopardy. Harris Trout investigates the police department and places Karen on suspension, demotes Carlton, and fires Psych and Buzz McNab.
Shawn (James Roday) and Gus (Dule Hill) dive into a world that's equal parts mystery and melody to track down an escaped playwright mad man, Z (Anthony Rapp, "Rent"), who six years earlier was deemed criminally insane after locking a critic in a back room of the theatre that he burnt to the ground.