Vick calls Shawn and Gus in after a group of fast moving and highly organized thieves pull a smash and grab robbery at a department store. It is the third such hit in a month and the cops have no leads. Gus is a little distracted. He's studying for his pharmaceutical rep recertification exam and is annoyed when some green goo from the store ends up on his study guide. As soon as Shawn takes a look at the security tapes, he knows immediately that the perpetrators were women. On the way out of the store, he sees skid marks across the floor and puts it together - the thieves are roller derby athletes.
Shawn suggests Juliet go undercover and join one of the two teams that weren't competing all the nights of the robberies. Using Juliet's new access, Shawn sneaks into the locker room, where he discovers a broken watch that matches one he saw broken on the security tapes in Fox's locker, a bottle of wheel lubricant in Wilde's locker, and a used ticket to a reggae cruise in Toxic Waste's locker. Shawn also notices that some of Juliet's new teammates have injuries that are more consistent with a robbery than with roller derby. Juliet spots Shawn and Gus and warns them not to blow her cover, but before they can leave, they are approached by two of her new teammates, Wilde and Fox. Juliet is then forced to introduce them as fans of hers.
Back at the Psych office, Juliet tells Shawn that she thinks she has a lead. One of the girls, nicknamed Toxic Waste, called her and said the team was impressed with her and thinks she'd be perfect for a big money making opportunity going down that night. Juliet thinks she's got an in on a robbery but Shawn, remembering seeing the cruise ticket in Toxic Waste's locker, tells her he's already eliminated her as a suspect. She has an alibi for the last robbery. Tonight is not what Juliet thinks it is. But Juliet pulls rank on Shawn and goes anyway, meeting Lassiter and her back up there. The gig turns out to be a music video shoot and Shawn covers for an embarrassed Juliet with Vick, saying the mix-up was his fault. While in police station, Shawn sees a list of the merchandise that was stolen during each robbery. Juliet is grateful to Shawn for covering for her with Vick, but in return Shawn insists that he now run point on the investigation. Juliet agrees and leaves for practice.
At the Psych office, Shawn recreates the merchandise lists, noting that the items stolen appear to be chosen at random. He also sees the green goo still on Gus' study guide and realizes that it matches the lubricant he saw in Wilde's locker. He knows for sure now that Wilde, along with Fox, was part of the robbery. Back at the arena, Juliet suspects the involvement of another teammate, Westwood, after she discovers her excuse for cutting practice is a lie. She looks around Westwood's area of the locker room and finds a couple of hand scanners, which she fingerprints. She calls Shawn to let him know what she found, then he and Gus tail Westwood and spot a body in the back of her truck. They call Lassiter after they see her dumping it into the marina, but when Lassiter has the water dredged, the body turns out to be a mannequin. It's not a total loss, though, as they find much of the stolen merchandise was dumped as well. Meaning, the thieves were after something besides the goods they took. As Shawn and Gus leave the dumpsite, Wilde is there and recognizes that Juliet's supposed fans are working with the cops. She reports this in a call to one of the other girls, also commenting that Westwood messed up and needs to be dealt with.
Shawn and Gus go back to the department store to investigate and discover that all the credit card applications get shredded on Fridays, the day after the robberies took place. Shawn calls Juliet and tells her that the thieves were using the hand scanners to steal credit information, and thus the identities of unsuspecting store customers. As they are talking, Fox and Wilde approach Juliet and demand she come with them. Shawn overhears that right before Juliet hangs up. Shawn and Gus rush down to the arena to help Juliet and discover Westwood's dead body in the back of her truck. Knowing that Juliet is in imminent danger, they rush inside to see that she is in the middle of a game. By watching Fox and Wilde, Shawn sees that the girls are angling to take Juliet out, in a violent and ultimately deadly way. He is able to stop the game in time to save her, and the cops take all of the suspects into custody.