A young woman named Allison comes into the police station claiming to have just escaped after being kidnapped and held by the notorious serial killer, Yin. Shawn and the police are loath to believe her since crackpots have been coming into the station for months making similar claims. Yet Allison proves she telling the truth by showing Shawn the picture of himself as a child standing next to Yang that we saw at the end of last season. With the cops on board, Allison takes everyone back to where she claims she was held only to find the house occupied by an innocent family.
Lassiter shows up to work one morning with his kid sister Lauren in tow. He explains that Lauren is a film student there to do a police documentary. Lassiter plays to the camera, trying to impress his sister with his "large and in charge" demeanor. Suddenly they get the call that there's been a murder at the zoo. Lauren films as officers prepare to leave for the crime scene.
After a criminal named Sergei Czarsky has his court case thrown out because of a critical error Shawn made while investigating him, all of SBPD is furious with Shawn. When Internal Fairs makes it a point to hold SBPD accountable for their mistake, everyone's job is in jeopardy. Shawn plays it off like it's no big deal, but Gus and Henry see otherwise. Vick then places Shawn on suspension, and makes the difficult decision to fire Henry.
The SBPD are on a stakeout watching a drug deal play out on their monitors. They are about to take down a criminal they’ve had their eye on for over four months. Then suddenly, through the monitor, the SBPD sees Gus walk in pushing a room service cart. Gus starts to distract the drug dealers. Shawn then jumps out of the room service cart and starts to snoop around. He finds a bag of prescription drugs, but gets caught almost right away. With guns pointed to his head, Shawn asks the drug dealers if they are selling these drugs out of this hotel room.
Shawn and Gus receive a mysterious email asking them to come to a Cinnamon Festival in Dual Spires, a town so small it's written in parenthesis on the map. After meeting many of the colorful residents, including Robert and Michelle Barker who run the local diner and Sheriff Johnson, who questions how they heard about the Festival since they deliberately keep it simple in their town, they make their way to the square where the Festival is being held.
Juliet surprises Shawn with tickets to Scare Fest, an event at the local theme park that hasn’t taken pace in 15 years. But Shawn already had tickets to go with Gus. Not wanting to let either one down, Shawn decides to go with both on separate nights, but doesn’t tell either one. Shawn already has enough tension built up with having to tell Gus about his and Juliet’s relationship. He doesn’t want either relationship to suffer because his attention is now divided.
Shawn and Gus receive an invitation from Desperaux to visit him in British Columbia, but there's a catch: Desperaux is still in prison. But after much convincing, Gus agrees to go with Shawn on the free trip. Fresh off sharing a kiss with Juliet, Shawn is faced with telling her his feelings before she leaves for the Amalfi Coast with her boyfriend Declan, and before he and Gus leave for British Columbia. However, Shawn misses his chance after McNab tells him that Juliet asked him with help with her passport, meaning she already left for Italy.
Shawn and Gus find themselves in the midst of a Bourne Identity-like hunt and chase after a U.S Government Spy named Nadia seeks their help in finding an agent who's been off the grid for quite some time. The agent she's looking for is Strabinsky - the only person in the world who has successfully erased his identity. Nadia needs to be erased too, as the government is chasing after her, trying to capture her for something she claims she didn't do. Shawn is quick to trust her because she mentions Ewan O'Hara's name, and because she's a sexy government spy.
Shawn, after a night in of drinking and listening to the chick-lit book series 'Internity' on audiotape, stops into a coffee shop with Gus before they are to be at a crime scene. Shawn, worse for wear, tells the barista that he will be getting his free since he will guess the trivia question again as always. However, he is beaten to the punch by Declan Rand, a handsome and charming man. Shawn wonders who he is as he leaves, but soon finds him across the street at their crime scene. Declan, it turns out, is a criminal profiler, brought onto the case by Chief Vick.
Shawn and Gus board a ferry bound for The Channel Islands. They’re volunteering for environmental cleanup, along with other nature lovers and a group of four prisoners on work detail. After Gus gets seasick, he and Shawn take a wrong turn, then run into CRAIG, the prison guard, who has been tied up and gagged. Craig tells them that the prisoners he was guarding escaped and are loose on the ferry. Shawn calls Henry and tells him the news. Craig, Gus, and Shawn find themselves in a standoff with the prisoners, who are demanding to be let go on the life raft.