"An Evening with Mr. Yang" is the sixteenth and final episode of season three. After eluding capture and disappearing years ago, the famed Yin Yang serial killer is back, and he's set his sights on Shawn.
Shawn and Gus are at a restaurant having lunch, or more like breakfast in Shawn's case, who is eating cereal in an attempt to break the "Breakfast Served Until-" barriers. As Shawn launches into his usual flirting routine with the waitress, Gus calls him on never taking relationships seriously. So Shawn, in an effort to prove him wrong, calls Abigail Lytar, his high school crush he reconnected with at his reunion, and asks her on a proper date. The guys are then summoned down to the police station. The Yin Yang Killer, a serial killer who was active when Henry was a cop then went silent, is back and wants to toy with the department again, this time singling out Shawn as his primary playmate. Mary Lightly, the police profiler, explains that Mr. Yang challenges the cops with the opportunity to save his victims by solving his riddles. Yang has just sent them another one, along with a stopwatch. They have an hour and ten minutes to solve the riddle and save his latest victim. Henry storms into the station, having heard that Mr. Yang is back and has set his sights on his son. He forbids Shawn to get involved with the case, explaining that if Yang has targeted him, he has also targeted the people he loves. But someone's life is in danger and Shawn has no choice but to play along. He figures out the riddle and is shocked to discover the target is the waitress he was flirting with earlier. They all arrive at the restaurant to find the waitress missing and a yin yang symbol with a streak of blood on her locker. Yang has left them another riddle and a stopwatch, this time giving them only eighteen minutes. Shawn realizes their next location is the police station, and he heads back to find Madeleine there waiting for him. She reiterates Henry's concerns, but Shawn tells his mom he's got this one and will wrap it up in time for his date with Abigail. Madeleine hopes he's right and wishes him luck.
Shawn catches up with the rest of the cops who have found a package from Mr. Yang. The killer somehow managed to get into the building and leave it for them. Mary opens the package to reveal another riddle and stopwatch along with a caged rat. The bottom of the cage is lined with newspaper classifieds that reference Shawn's old cases. Shawn, Gus and Mary are able to piece together the clues that send them to a moving train. Shawn and Gus jump on to find a stack of Polaroids this time, with the riddle and the watch. Shawn puts together the clues to discover Yang is sending them to yet another location, the boardwalk near the Psych office. As soon as they get there, a phone starts to ring for them. Shawn, realizing the phone didn't start ringing until they got there, refuses to answer it, knowing Yang is watching them. He sees movement in their office and takes off, but by the time they get there, Yang is gone, leaving behind a picture of the waitress, bound and gagged, and a hand ritten message on the back. Mary, whose respect for Yang's ability is now shared by everyone, explains the killer is giving them a second chance to save the waitress. But Shawn refuses to keep playing Yang's game, insisting it's getting them nowhere. He quits the investigation, forcing Mary and the cops to continue on without him.
Back at the police station, the police get a fax from Yang, and, realizing the killer must know Shawn quit, figure out the new riddle is directed at Lassiter who deciphers it to reveal a hotel and room number. Meanwhile, Gus and Shawn, who only pretended to quit the investigation to circumvent Yang's game, head back to the restaurant where it all started. They figure out that Yang used the waitress' car to abduct her, so if they find the car, they find the girl. Shawn calls Lassiter to let him know, but he is already at the hotel and her car is in the parking lot. Shawn and Gus race over there and they bust into the room to find the waitress alive, tied up with a note stuffed into her mouth. Shawn looks around the room and sees the purse Madeleine was carrying earlier at the police station. Yang has exchanged the waitress for Madeleine, forcing Shawn's return to his game.
Shawn deciphers the latest riddle, sending everyone, including Henry, to the drive in theater. Figuring since Yang used his victim's car once, he probably did it again, they start searching the cars for Madeleine's rental. Shawn finds his mother in her car with a laser sighting pointed at the back of her head. He waves the cops off, but Henry is able to duck down behind the vehicle. Lassiter, Juliet, Gus, and Mary take off to find the source of the laser but Shawn sees it's a decoy, and he and Henry stay behind. When the cops get to the projection booth, they ask Mary to explain the motivation for the fake out, but for the first time, Mary is thrown, saying this is not Yang's usual game. Back at the car, Shawn sees that his mother is wired to a bomb. Madeleine is able to indicate Yang's location to Shawn, and, looking over, he is surprised to see a woman holding a detonator, calling him over. Shawn heads over to Yang, while Henry stays behind with Madeleine. When Shawn gets into the car with Yang, she congratulates him for getting there on time and being the first person to win her game. She says she could have killed Madeleine hours ago but she wants Shawn to like her because they will be working together again. The cops now have them surrounded, and Shawn tells Yang it's over, but she replies that she is going to write a book from prison and she wants Shawn to write the foreword. She then hands him the detonator and turns herself in. Madeleine, who is now safe, insists Shawn keep his date with Abigail, who has just arrived. Shawn leaves her to get popcorn for their date where Juliet corners him alone. She tells him how impressed she is with him, then, finally cutting through all the complications, asks him out to dinner. A stunned Shawn tells her that her timing is horrible and that he is already out with someone. He then leaves her, returning to Abigail, finally ready to take her seriously after thirteen years of making her wait.
- The title evokes a one-man show or similar, a presentation of skills and personally chosen performance pieces by an actor, artist or celebrity.
- Foreshadowing: When Shawn says to Yang (in the car) that he's her Yin, she doesn't give a response. Her not agreeing to his statement foreshadows the revelation in "Mr. Yin Presents" that she had a partner, "a Yin to her Yang" -- Mr. Yin.
- At about 39:30, Juliet says “Get out there. She’s not gonna wait forever.” in reference to Shawn and Abigail’s date. This shows that Juliet knows she was too late in asking Shawn out—he didn’t wait forever.
The gallery for An Evening with Mr. Yang can be found here.