Gus pulls his car up with Shawn inside of it. Shawn stays in the car while Gus deposits a check, because he says it it not a two-man job. He's only in there a few minutes before a woman spots a gun in the jacket pocket of another customer (Alan Ruck). She screams and the man is forced to pull out his weapon and take everyone in the bank hostage. One of the tellers hits the silent alarm button, bringing the cops screeching up outside the bank next to Shawn, who is unaware of what has just transpired inside. When Lassiter and Juliet inform him of the situation, Shawn is immediately worried for Gus. The cops quickly set up a command center and are able to access the security feed from the bank. Shawn sees the man holding a gun on the bank manager Nathaniel Greslin (David Bloom), stealing something from a safety deposit box. But before Shawn can investigate further, the SWAT team arrives and their negotiator, Cameron Luntz (Gary Cole), takes over. Shawn steps away from the crowd and dials Gus' cell phone. Inside the bank, the gunman hears a cell phone ring and becomes agitated. When he asks whose phone is ringing, Gus doesn't move, but he is quickly called out by another terrified hostage (Dean Paul Gibson). The gunman destroys Gus' cell and confiscates the phones of all the other hostages. Luntz calls into the bank to start negotiating and is quickly able to get the gunman to give up his name, Phil Stubbins, and to agree to accept pizzas for one of the hostages who is diabetic. Shawn is frustrated to be marginalized by Luntz, and tries to convince Lassiter and Juliet to act on their own. Lassiter refuses, saying it's protocol and Juliet defends Luntz to the point where Shawn is able to deduce that they are dating. Unable to get any traction with them, he goes directly to Vick and Luntz, who has since found out that Phil owes money to the IRS and his house was recently foreclosed on. Shawn tries to convince him to send him into the bank, saying he can divine more information from the situation than another cop. But Luntz has had enough of Shawn, and makes him stand behind the barricade with the spectators. As Luntz is about to send the pizzas inside, Phil calls, suspicious that the person coming in is a cop. He insists someone from the crowd bring them in, so Luntz is forced to use Shawn after all.
Once inside, Shawn sees that Phil has the safety on his gun and realizes that Phil is not the person the cops think he is. He asks Phil to take him to the bathroom, where he tells Phil he's psychic, and to prove it, he repeats back to him some of what he learned from Luntz. He tells him he knows he's not really a bank robber and Phil, relieved, tells Shawn what he thinks he already knows - that some men kidnapped his wife and forced him to steal diamonds from a safety deposit box. The heist went wrong and Phil doesn't know how to get out of it. He says he thinks one of the bad guys is actually inside the bank, watching him, making sure he complies. Shawn says he will help Phil, then calls Luntz to explain the situation, but Luntz doesn't believe him. Shawn hangs up and calls Lassiter, who agrees to send McNab to Phil's house to verify his story about the wife. To stall for time, Shawn takes Phil into Greslin's office and has him call Luntz with a list of ridiculous demands. While in the office, Shawn spots a list of recent home foreclosures on the desk. He then rejoins the other hostages where Gus asks Gresling to recount what happened when Phil entered the bank. Gresling's story does not match what Shawn saw on the security feed earlier. Shawn leaves them to check on Phil, who tells him the police are meeting all his demands. Shawn realizes that is just a ploy on Luntz's part, and is barely able to get Phil out of the way as a sniper takes a shot at him. He saves Phil's life, which now makes him a pariah to the rest of the hostages. Shawn tells Gus he thinks Phil's wife is being held at one of the foreclosed houses and convinces Phil to let him out of the bank. But before he goes, he shares his suspicions of Gresling with him.
Once outside, Shawn "psychically" leads Lassiter to the addresses he saw on Gresling's desk and they are able to rescue Phil's wife Joanna (Jhene Erwin). But Phil is unable to keep from accosting Gresling in the bank and is knocked out by Gresling's mystery partner, the one that had secretly been monitoring Phil's progress. Gus comes across this exchange and is then held at gunpoint with Gresling and Phil, by the man who earlier outed him for his cell phone, Morgan Phelps. Shawn, Lassiter, and Juliet rush back to the bank but Luntz has already stormed it and freed the hostages, allowing Phelps to escape in the air vent Shawn "psychically tells Luntz that he is it the sewers.But Shawn sees that Phelps didn't go far - he is hiding in the air ducts, where Lassiter apprehends him. Later that night Juliet pays a visit to the Psych office all dressed up, to return Gus's shoes. Luntz had to cancel last minute because he was in the sewer. Juliet and Shawn then go out to eat together.
- The title is intended to evoke the 'A man walks into a bar' opening of many jokes.
- A pineapple appears when Shawn has to go to the bathroom in the bank. The Snack Delivery System has a pineapple shape carved into it right above the Hot Dogs.
- The actor who plays the bank robber Phil (Alan Ruck) is most famous for his role as Cameron in Ferris Bueller's Day Off. Naming the hostage negotiator Cameron is most likely a shout out to this (especially considering Psych's affinity for '80's movie references).
- This is the only episode that not only doesn't include a flashback at the beginning of it, but also the only time where Shawn and Lassiter actually work together AND Shawn even helps him apprehend the criminal.
Shawn: Just once, can you grab life by the little Lassiters and follow your instincts? I know you don't like my methods. I know you don't like *me*. But we are pressed for time, and I'm telling you, I am vibing like crazy! Can we screw protocol and get the hell out of here?
Lassiter: You take shotgun.
Shawn: You are so sexy right now!
The gallery for Gus Walks into a Bank can be found here.