The movie opens with a younger Carlton Lassiter and his dad out in the wilderness. They are exploring when Lassiter asks his dad if he will ever grow a beard. His dad he is a Lassiter and he will grow a face wig, like the men before him. Mr. Lassiter says it has been happening for generations.
They continue their hike when Lassiter turns around, only to see his dad gone. As he screams, we see Lassiter being attacked in an ambush. He tells the attacker he as a family when he is shot once more..
As he is waiting for help, he sees his dad again, asking him to think and remember why he is there. He is shot again and finally brought to the hospital.
Later on, Lassiter wakes up with Gus and Shawn screaming surprise. Lassiter asks what is wrong with them and why they have Chief Vick’s dog. It turns out they took the dog and came to a little agreement. Shawn also points out the dog is a rescue dog to rescue Lassiter from is own handsomeness.
The dog is trying to eat Lassiter’s foot when Dolores the nurse walks in. She sees Lassiter has company. She questions if the dog is a therapy dog and they give her a shirt, which claims Morrissey is indeed a therapy dog. Delores says it is a doctored Theraflu shirt. Shawn says she is good and introduces himself and Gus (as Bill Poopingtons) Gus calls for a sidebar and reprimands him for the name. He also requests there be no more embarrassing nicknames. Shawn makes an off color ‘don’t be’ joke and says that they need to continue the bits they have been doing for the past ten years. They finally agree to argue until they land on a name he likes.
Shawn reintroduces himself and Gus as All The Pips In Once. Gus accepts. Delores asks to talk to them privately. They follow her out of the room, but not before Shawn makes an off color joke about something in Lassiter’s bed.
Gus (who is now going by Jermasesty) and Delores flirt a bit while discussing Lassiter. She wants to know why they are really there and they explain Lassiter has seen some strange things, such as ghosts, black jello and eerie voices. Delores said he never said anything to her and they say that the men made a pact to keep it between them. Shawn says he cannot tell his wife and Gus was he cannot tell his girlfriend and he is avoiding her calls. Shawn says that in reality, he is avoiding her calls because an app for Jamaican emojis messed up his phone.
Shawn says Lassiter is afraid he is going crazy and it might cost him everything. Delores counters that he only remembers a silhouette of the shooter to meds and a massive stroke. She says she knows the ex black guy/goofy white guy act like the back of her scrubs and they can help by acting like grown men.
After Delores leaves, Shawn calls him out on her apparently hitting on him. Gus says he is with Selene now and he cannot keep up with every shorty who wants what they cannot have.
The guys go back to see Lassiter, who wonders where they were. Shawn says Gus insisted they make a Jamba Juice stop. They wonder where the dog is an Lassiter tells them that he ran away after stealing his jello.
Shawn wants to pass on helping Lassiter due to the fact that they have to lie to their ladies. They say he is just really high and imagining things when the dog comes back with a human hand in his mouth. Everyone freaks out.
Shawn and Gus discuss what to do as they mail the hand to Woody. Gus argues that they cannot ship a living thing, with Shawn countering that it is dead and they need to find the rest of the body. Gus says their stuff is back in Psychfransico. Shawn says but is it….
After bit more arguing, they go back to the Psych office. Shawn says they are home and Gus makes the Chewbacca sound. They go inside, only to find it is a pop up cat cafe run by what Gus thinks is a young girl and Shawn thinks is someone much older. Shawn introduces them (with Gus being Ding Dong Ditch, Claude O’Dirt, Big Poppa Pump and finally…Lemona-lemona-lemona-lime) and they continue to give her a hard time about her age and her being in their old office.
She tells them to see the landlord, who turns out to be Henry. He says that they never cancelled their lease, so he took it over and sublets it. He says he is rolling in disposable income and asks why they are bothering his clients.
Shawn says they are back to get some things they left behind. Henry says they left behind a slow cooker with a three pound roast in it and almost This Is Used the entire neighborhood. Shawn asks why he watches that show when he can watch the newer one on ABC.
The Cat Cafe owner knocks on the door, saying she is allergic to the cats. He says that is not his problem. Shawn asks if Henry can help them for Lassie and Henry agrees.
Lassiter has another flashback when he is surprise again, this time by Juliet. He says he can see all her teeth. She says she is so excited to see him and she misses him. He is surprised and she says she is really there because she saw a mugshot of the guy (Kessler)suspected of shooting him.Juliet says this guy made a full confession, but Lassiter wonders if it is the right guy. He is frustrated because he cannot remember. Juliet also points out a bullet is missing and this guy never mentioned a second gun. She questions the confession too and says she wants to help.
Lassiter sends her to do his errands.
Shawn, Gus and Morrissey try to find more clues as to whom the hand belongs to, while Lassiter and Juliet share an emotional moment. she promised to return with everything done and bearing chocolate. She also gives him his badge, thinking he might want it. They agree to be honest, but he clams up when questioned.
Shawn and Juliet talk on the phone and realize they are both in Santa Barbara. She wants to cancel, as does Gus, but Shawn insists they meet up. They hang up and Shawn thinks there is something wrong. He thinks he let her down and vows to be the man she deserves.
Juliet goes back to the crime scene to investigate (with flashbacks playing) and finds a bullet hole and a woman who has been shot. Juliet promises not to shoot and that she needs medical attention. She also tells the woman she needs the bullet in her leg.
Shawn and Gus hurry home to make Juliet dinner, which consists of popcorn, candy and as Gus puts it, the Charlie Brown Thanksgiving Dinner. As they prepare for the dinner, Gus’s phone goes off and he says there is no way he can answer the phone.
Juliet arrives and Shawn forces Gus to hide.
At dinner, they discuss the Lassiter situation, but are not specific to what they are really doing. Shawn also volunteers to do the things on Lassiter’s list, but tonight they will snuggle with her Snuggie. He goes to get it, but finds Gus in the drawer wearing it. The two bicker and Shawn goes to tell Juliet he cannot find the Snuggie when Gus’s phone goes off. She is a bit suspicious, but he says Gus left the phone there. He sends her to find the Snuggie while he tells Gus to shut the phone off.
It turns out Woody is calling. He is eating the meats they sent with the hand and says there is a usable fingerprint for someone named Devon Tileback. Woody thinks he died by suicide, which makes Gus think it is an open and shut case. Shawn disagrees and says they have to go to Santa Barbara to investigate. They confer a bit and then Shawn goes to Juliet.
Lassiter has another flashback, only this time to be greeted by Morrissey. He admits to him that he cannot walk and feels as if he may end up being a burden to his family. He looks outside in his wheelchair when he thinks he sees a bleeding man. He asks the dog if he is crazy when his father appears to him, saying that he is not crazy, he is a Lassiter.
Lassiter tells him he thought he said to leave him alone. His dad says they have some catching up to do.
The next day, Shawn and Gus talk to Lassiter about what he saw. However, they question what he saw because the hand is not connected to the case and Lassiter’s only witness is a dog. Lassiter convinces them he needs them and they agree, mostly because he said please.
Juliet is at work when Selene appears, wanting to send out a missing persons report for Gus. She says she cannot get in touch with him. Juliet says Gus left the phone at their house when they were in Santa Barbara, upsetting Selene, because she had no idea he was there. She is also upset when Juliet brings up Delores. Juliet tells her to stop worrying as she goes to get Kessler to recant his confession.
Shawn and Gus continue to investigate in the hospital (while eating flavored ice chips) when they run into Dr. Hershel, who questions them and confiscates the ice chips. They question the doctor, who says they are doing everything to help him. However, he thinks is is normal for someone who experienced extreme trauma. He tells them if they come again to stay in the visitor sections. He leaves and the guys steal more ice chips before leaving themselves.
Chief Vick talks to Juliet about being up for police commissioner. She questions Juliet on what is going on with finding Lassiter’s shooter and tells her she can investigate if she clocks out and is honest.
Juliet goes to leave when Selene arrives, saying she is coming along for the ride.
Shawn and Gus are at the cat cafe Psych office investigating when they realize their suspect has been frequenting a Vikings Ice Bar. The go to investigate.
Meanwhile, Juliet goes to question Kessler, with Selene in tow. He initially refuses to talk to her, but she convinces him to talk….until Selene interrupts, messing up the interrogation.
Shawn and Gus arrive at the bar to investigate. The bartender says he owed a lot of money and was beginning to lose it. As they talk, they are approached by the owner Ova. He asks if they have been to Norway and they say they went with Ewan. Gus says they do not talk about that. Ova gives them vodka and sings to them before they cheer.
Shawn asks about the ‘bearded Daryl Hannah,’who turns up to be the owner’s son. He tells them to stop gawking.
Per (Ova’s son) and Gus are in the bathroom when Gus’s phone rings. He tries to answer, but ends up taking a picture and tweeting Per with his pants down. Per is very angry and threatens him with a knife. Gus runs out and tells Shawn they need to leave. Shawn is confused and Gus tells him he will confess what happened on his death bed.
At that moment, Per chases them with other bar patrons, leading them to get on his motorcycle. They crash and are found by Devon, who is not dead, but scared other people may die soon if they don’t leave this alone. They question him when he is shot and killed for real…..leading to them to play dead.
McNab shows up at the crime scene and asks why they are there. Shawn and Gus explain everything, which confuses McNab even more.
They continue to question each other when Juliet shows up with Selene. McNab is still confused when Shawn and Gus go to hide.
Juliet goes to talk to McNab, who relays what Shawn told him. Selene comes up and McNab confuses her with the nurse Gus mentioned before. Selene gets angry over this.
Meanwhile, Shawn and Gus crawl through Juliet’s car, where Shawn finds a pregnancy test. He is shocked, but escapes just as Selene takes Juliet’s car. Juliet goes to follow her in McNab’s car.
Shawn is freaking out at the cat cafe shop. Gus tries to get him to calm down when they get a text from Lassiter saying Wilkerson (comatose guys in wheelchair) is faking it.
They go to talk to Henry. Shawn thinks Henry took his mustache collection, causing them to fight.
Gus gets them back on track, sayin Lassiter is brilliant and has a sharp mind, so they should believe him.
They go back to the hospital to question Wilkerson. After they do the introduction game, they try and prove Wilkerson is lying by tickling his feet and touching him. Dr. Herschel catches them and demands to know what is going on, ultimately kicking them out.
Delores comes by to see what is happening and as the doctor leaves, they fill her in. They tell her they are on to the ‘good doctor,’ but Delores says they are off base and sends them on their way, but not before kissing Gus on the cheek.
Back at the office/cat cafe, they continue to discuss the case. Shawn also finds the mustache collection. He tries to impress the cat cafe owner with his Spanish impression, but she threatens to call the cops.
Woody arrives! He goes off on a tangent when the guys tell him he needs to focus and find a way to get in on the inside. He pretends to be a doctor when he enters the building, but cannot spell his name, causing the receptionist to be suspicious.
Chief Vick goes to her police commissioner interview, but cannot focus because she got the information on the case she needed. She ultimately leaves and recommends someone else for the position.
Shawn, Gus and Woody reconvene to discuss what is happening. Woody took Lassiter’s pills….literally and has one lodged in his throat. As he coughs it up, Shawn goes to get it (discovering it is a chicklet) when he finds stuff for an emergency patch job. They come to the conclusion Dr. Hershel is up to no good.
They tell Delores what is going on, but she is afraid to help and risk getting into trouble. She sends them to Lassiter’s room and tells them to stay put. After she leaves, Shawn sends Gus for snacks and goes to talk to Lassiter about Juliet’s pregnancy and being a father.
Gus runs into Henry, who is concerned about Shawn. Gus tells Henry about the baby and Henry goes to find Shawn to make up and have a heart to heart. They then go over Lassie’s list, when they see an indentation in the paper They realize there is a silent partner that was present the day of the shooting.
Henry goes to investigate when Gus comes back with a ton of food.
Later on, when everyone is asleep, Shawn goes into the hall find a baby Mary Lightly (in his dream). He thinks it is him questioning fatherhood.. Mary acts like a baby and demands Shawn sing him to sleep. Gus joins them and Shawn says he is the one ready for fatherhood. Mary continues the baby act when they spot Wilkerson trying to escape. Gus goes to chase him when Shawn goes to talk to Mary, who has disappeared.
Gus is holding down Wilkerson and thinks he is a merman. They finally get Wilkerson to confess that he is able to walk, but has weakness on his right side. Shawn realizes they are not dreaming, but they were all drugged via the ice chips. Wilkerson says he is a dead man walking and confesses to everything he did with Devon. It turns out they witness the shooting of Lassiter, but have no idea who did it. He realizes he has to go, but they convince him stay.
It turns out Woody is still there and he found more evidence,which leads them back to the ice bar. When they enter, they see Juliet, who is mad at them for sneaking around. Shawn worries about her, but she insists she is fine. Chief Vick is also there with Morrissey, saying they found the gun and final bullet.
Juliet tells them Ova is involved and they all realize he is the shooter and Dr. Hershel is the inside guy. Morrissey begins barking and they open a freezer to find Ova is dead.
They go into the bar and are held at gunpoint by Per. It turns out that Per waited his whole life for this moment and he changed the deal. This led to him shooting Lassiter and he made sure he got into the right home so he could be watched.
At that moment, Selene arrives, still babbling over the nurse. Per goes to shoot, but Shawn says he cannot shoot his pregnant wife. Gus helps protect her, but Juliet threatens to shoot them with this weird distraction. It turns out she is not pregnant, but Selene is! Everyone is thrilled, except Gus who faints. This leads to the women holding Per at gunpoint.
Delores gives Lassiter pills that will kill him and they realize she was the bad guy all along. As she confesses the was the one behind it all as she poisons his IV bag. He goes into a sleep when his dad arrives again, telling him not to give up. Delores realizes this and says he will see his dad real soon. His dad, fr his part says he is sorry for dying, but he is proud and never missed a moment of his life. It turns out he died of a blood clot during a bypass. He convinces Lassiter to continue to fight as Delores tries to kill him. Lassiter grabs one of his hidden guns and shoots the IV bag. His dad says he has the guns hidden while Lassiter says Delores has the right to remain silent.
Selene, Gus and Shawn discuss the baby. She and Gus propose to each other while Chief Vick says she is going to be a godmother. Juliet scoffs that she is her best friend. Everyone cheers for the new engaged couple and parents to be. However, it turns out Selene is still married.
Woody plans on staying at the home, but his identity is uncovered. Shawn and Gus are also kicked out.
The movie ends with Juliet and Henry taking Lassiter to see Marlowe….and Lassiter walking over to her on his own. They hug as Lassiter says goodbye to his dad one last time.