Mr. Yang (also known by her actual name, Ms. Rotmensen) is a serial killer who made her first appearance in "An Evening with Mr. Yang". She returned in both "Mr. Yin Presents..." and "Yang 3 in 2D". She was killed in "Psych: The Musical" saving Shawn's life. She is portrayed by Ally Sheedy.
Mr. Yang a serial killer who supposedly murdered her first victim in 1995. Her counterpart and former partner is Mr. Yin. That year, she was said to have killed six people after a game of cat-and-mouse with each of them. Over the next 14 years, she was to also kill two others and was still not caught, nor her identity revealed.
She met Shawn when he was about nine years old (he passed her on his bike ride home while she was taking out the trash) and they had a conversation. When Shawn's mother went looking for him, Yang was able to persuade her to take a picture of them together.
For Shawn this was the end of the incident (he didn't even remember the incident until it was brought up 22 years later) but Yang grew attached to him, possibly because his happiness first opened her to the possibility of a stable happy family.
An Evening with Mr. YangEdit
In "An Evening with Mr. Yang", Mr. Yang has returned, this time, to play her game with Shawn. After Henry's adamant protests to the contrary, Shawn accepts her proposition, vowing to bring her to justice. She first kidnapped Shawn's and Gus's waitress and held her hostage. After leaving several cryptic clues for Shawn, the hostage was finally returned but replaced with Shawn's mother, Madeleine. After strapping a bomb to Madeleine, Yang sat and watched as the Santa Barbara Police Department swarmed a drive-in theater looking for her. Shawn found her car, and she finally came face-to-face with her target. She revealed to Shawn that she was going to write a book about them, and was finally arrested.
Mr. Yin PresentsEdit
When Shawn and Gus speak to Mary Lightly (a psychologist who helped bring Yang to justice) a year later, in "Mr. Yin Presents...", he reveals that it would be impossible for Yang to work alone, and proposed that she was working with a Yin. He discerns this from Yang's book, entitled From Serial Dater to Serial Killer: How Murder Kept Me Skinny. Mary's theory proves to be true, and Shawn, Gus, and Mary proceed to visit Yang in her tiny cell at an asylum. While there, Yang admits to working with a Yin. She says, "If you think I'm sick, you ain't seen nothing yet." This proves to be true, as Mr. Yin (representing chaos) has no rules. Mr. Yin then goes on to kill Mary, and then play a "game" with Shawn. He kidnaps both Abigail and Juliet, then forces Shawn to choose which to save. In the end, both are saved.
Yang 3 in 2DEdit
Yang's story is concluded in "Yang 3 in 2D". It is revealed that Yin is her father, and while she often aided him, she never killed any of the victims herself. She never wanted to be a serial killer and wanted a life of family and friendship much like Shawn's. In the end, her father becomes her first true victim. Yang tells Shawn she will remain in prison for all of the Yin/Yang murders, not knowing any other existence.
Psych: The MusicalEdit
In "Psych: The Musical", Yang is brought out of jail by the SBPD to help track down the escaped Z. She forces them to sing for her before she gives them information. While Lassiter, Juliet, Shawn, and Gus are chasing Z, she escaped her guard and ran. She continued to Skype Shawn and help him with clues if he sang until he finally tracked her down and accused her of killing Elisa, Z's love. Yang was upset that Shawn appeared to be losing his special gift, as this was untrue, but when Shawn was attacked by the real killer and hung from a rope, she attacked the man with a knife, driving him away and saving Shawn. However, during the scuffle, she was stabbed, and she dies. As she dies, she sees her "angel", Mary, who implies she won't be getting into heaven, but he said he "knows a guy who knows a guy" and he'll try to get her in.