Gus' supervisor, Frankjim Ogletree, demands that he quit moonlighting at Psych, lest he face termination. The vice-president of Gus' pharmaceutical company, however, decides to hire the duo as his wife believes that their home is haunted.

Shawn and Gus attend their high school reunion. Shawn sees a body fly past a window, but on further inspection the body has vanished. When Gus assumes the worst, and Lassiter refuses to help, Shawn seeks assistance from Juliet.

After eluding capture and disappearing eight years ago, the famed Yin Yang serial killer is back, and he's set his sights on Shawn.

The Yin/Yang trilogy comes to a thrilling close as Shawn and Gus race to save a woman kidnapped by Yin. Only this time, they are forced to use Yang's knowledge of Yin to solve the case by allowing her to accompany them on the investigation.

Gus gets a girlfriend, and Juliet goes undercover on an online dating site to catch a killer while Shawn tries to holster his jealousy!