Chief Vick goes over a case with Shawn, Gus, Lassiter, and Juliet involving stolen oxygen tanks from a medical supply company. Lassiter and Juliet suspect the criminals are going to sell the tanks for a profit, however after they learn the street value isn't that high, they think perhaps this crew is up to something bigger.
Juliet's 30th birthday coming up. Shawn notices she has received a gift in the mail from her estranged father Frank O'Hara. Shawn is excited at the prospect of meeting Juliet's dad, but she quickly informs Shawn that she wants nothing to do with him, and that he isn't "presentable." Shawn sees the return address on the card Frank sent her and from there, Shawn decides to visit Frank in LA so as to make amends between he and Juliet.
Shawn is very impressed with Frank O'Hara, who at first meeting, appears to be a mansion-dwelling millionaire. Shawn bonds with him almost immediately and goes on to tell Frank that he is dating his daughter and needs to fix the broken relationship Frank has with Juliet. Frank takes this to heart and invites them into his richly decorated abode. Shawn tells Frank that he is a psychic and proves it by psychically revealing he knows Frank is about to embark on a yacht vacation. Shawn is right and Frank is impressed.
Back at the SBPD, Shawn tells Juliet that he fixed things with her dad and that he is coming to her birthday party. Juliet is pissed to hear this news and tells Shawn the truth about her dad - that he is a con man and a criminal, and the mansion they were in wasn't his. Shawn is shocked that Frank duped him, but also intrigued to figure out Frank's game.
Meanwhile, the masked men who stole the oxygen tanks from earlier break into Lompoc Prison and bust out a known safe-cracker named Jimmy Fitz.
When the SBPD gets wind of the prison break, Frank O'Hara has already arrived at the station. Shawn and Gus approach Frank first to ask him why he lied to them. Frank apologizes and explains that it was Shawn's influential words that convinced him to turn a corner, and to mend his relationship with Juliet. But the second Juliet sees Frank at the station, she is not pleased.
Lassiter and Juliet explain to the team that the criminals used the stolen oxygen tanks to cut through the wall that lead to Fitz's escape. Lassiter believes that breaking Fitz out was their endgame. Frank chimes in, saying he disagrees. He believes the criminals needed Fitz's skills as a safe-cracker for the much bigger score they have in the works.
Juliet has a sidebar with Shawn, Gus and Frank. She is upset at Shawn and Gus and wants Frank to stay out of her personal life as well as her professional life.
But Frank turns out to be right about Fitz when Lassiter gets a call saying the criminals have just stolen a bunch of construction equipment. Frank believes the criminals are going to use the stolen equipment for another break-in in the next 24 hours. Frank also tells Juliet to keep a close eye on the leader of the crew, Chad Emigh.
Later, Shawn gets a call from Juliet saying that there was some complaints of construction noise downtown. Believing that Frank wants to get back in the good graces of his daughter, added with the fact that Frank knows a lot about the criminals the SBPD is investigating, Shawn decides to hire Frank.
They show up to the scene and realize that a series of underground vaults were broken into and an entire safe was stolen. Juliet is furious when she sees Shawn and Gus have hired Frank to be on the case, working as a consultant for Psych.
She is even more upset when she sees Frank basically holding court in the SBPD, telling her colleagues his theories on why they stole the safe. Shawn jumps in and says it must have been for Jimmy to have something to practice cracking until they make the real score.
Frank makes a suggestion that leads Shawn to predict that the criminals are after a 1943 bronze Penny worth 2 million dollars that will be showcased at the Coin Expo that just happens to be rolling into town.
The SBPD question Sheldon Gates, the head of the Coin Expo. He tells them that they have taken all necessary precautions with security for the coin. They even have a decoy coin made for extra protection. Frank suggests that in order to determine if the Coin Expo is the target, they need to see if there is an Inside Man working the coin show.
Shawn suggests the Inside Man is the Electrician – a temporary employee hired on after a blackout. Frank convinces Juliet to question the electrician, as he believes she's got the skills in her to get him to crack. She does, and sure enough, she gets the electrician to admit he was hired by a crew of guys and overheard them saying they were going to hit the Expo to steal the penny.
From this, Vick orders that the entire SBPD stakeout the Expo to ensure they catch the criminals. At the Expo, Frank is certain he spots the criminal mastermind undercover and suggests Lassiter order a take down. He does, but the supposed criminal is clean, and Frank was wrong. Frank is starting to crack under the pressure. He isn't finding the culprit like he said he'd be able to.
Just then, Lassiter gets a call telling him that a store called "Prestige Safe Deposit" was just robbed. Shawn determines from this that the criminals realized that the real penny was at Prestige and not at the Expo.
Frank is defeated and embarrassed that he was wrong, so he decides to take himself off the case. They look at the surveillance photos of the crime that took place at Prestige. Shawn "envisions" a birthmark on one of the thieves necks which leads him to flashback to the same birthmark he saw on Frank's sidekick, Kato, whom he met at the mansion. From this, Shawn realizes that it was Frank who engineered the coin con and was the actual coin thief all along.
Shawn tells Frank that he needs to return the coin and make it right with Juliet or risk permanently damaging their relationship. Frank tries to explain his bad behavior, saying that once he was in the SBPD, and he saw the coin opportunity, he couldn't help himself, and decided to engineer the con on the fly. Shawn tells Frank that he will give him time to return the coin and make it right with Juliet. But that is Frank's decision.
Later, Juliet gets a tip about where the coin is. She interrogates the supposed criminal, Chad, just taken into custody after they found the penny in his hotel room. But Juliet quickly realizes that the coin was planted in this guy's room, and that it was her father, the real thief, who planted it there on purpose so that Juliet would get credit for the take down. Since they have no evidence to support an arrest, they have to let Chad go. Turns out, Chad's crew had absolutely zero plans for robbing the expo and that it was Frank who masterminded the whole thing.
A fuming Juliet lets her dad have it and tells him all the reasons why he failed as a father to her. She tells him she never wants to see him again and leaves in tears.
Shawn and Gus are totally defeated by this whole situation. Shawn flashbacks to evidence from Chad's hotel room that leads him to believe that Chad and his crew are going to rob The Santa Barbara Bowl. Juliet confirms that they did find a series of ticket stubs in Chad's hotel room, so the SBPD heads to The Santa Barbara Bowl to stake it out.
While in the stake-out van, Frank shows up. He apologizes to Juliet for everything and tells her that he, in fact, was present at many of her childhood functions, but he never told her because he didn't want his presence to embarrass her, and that Juliet has made him so proud over the years even though she didn't know he was there to witness her accomplishments. Juliet lets this sink in. She is touched and a bit shocked to hear Frank telling her this. Frank leaves the van and immediately notices a suspicious man in a red ball cap and grey sweater. He alerts the team in the van.
Shawn then notices a radio van that looks suspicious. They check the supposed radio station and sure enough, it doesn't exist. The van is the criminals' getaway vessel! Frank has a plan – to let the criminals carry out the act, but when they get back to the van, they won't know that it is Lassiter who is driving them to the police department to be arrested. Frank's plan works, the thieves are finally caught, and Frank has made the first step in redeeming himself in the eyes of his daughter. Their relationship is in no way fixed, but it is a step in the right direction nonetheless.
Juliet admits to Shawn that his heart was always in the right place, and is happy to have her dad there to celebrate her 30th birthday with. Frank confesses to Shawn that an associate is 'restoring' the real penny to police custody as they speak.
- The title is drawn from the old adage, "In for a penny, in for a pound", suggesting that one should commit wholeheartedly to any endeavor one bothers to undertake, although here the numismatic penny at the heart of the case is clearly equally significant.