The show opens with a flashback to 1987: Henry, Shawn, and Gus are checking out at the supermarket. Shawn is trying to convince his dad not to make him put back one of his candy bars. Then he tries to get Gus to check out first, so he can con Gus into giving him his change so he can afford the extra candy bar after all. Henry and Gus call him out, though, and make Shawn go first. The cashier starts the transaction and a siren goes off. Shawn is the one-millionth customer, and he won prizes: a gift certificate and a cool bike. Shawn wants to know if he can use one of his gift certificates right now. The cashier tells him sure, and he buys ALL the candy bars at the checkout stand. Gus and Henry look on in disgust and disbelief.
In the present, Shawn's on a date with a pretty brunette. As the evening wears on, it becomes apparent that the girl has recently had a breakup. The girl thought her boyfriend was cheating on her, because she caught him going through her stuff and lying to her about his whereabouts. Shawn, reading the clues, knows the boyfriend was actually getting ready to propose, and tells her so. She immediately walks off to call her boyfriend. Shawn, now alone, turns around to see a falling-down drunk Lassiter sitting alone at the bar. Lassiter is depressed. For one thing, it's the two-year anniversary of his separation from his wife. For another, he knows Shawn isn't psychic but he doesn't know how he solves those cases so easily. Lassiter used to be a good cop, but now he is ready to give up. Then he tells Shawn about a new case he has, about an apparently healthy astronomer who died of no apparent cause, but he can't figure it out, and the case probably go unsolved. Shawn tries to bolster Lassiter's confidence, but a depressed Lassiter says Shawn might as well take his handcuffs; he's giving up. Shawn's date runs up, ecstatic, hugs him, and tells him she just got engaged. As she leaves, Shawn turns to offer some more words of encouragement to Lassiter, but he has fallen off his bar stool and passed out.
The next day at the precinct, Shawn stops by to see if Lassiter is okay. Lassiter is in total denial about the whole incident. Shawn lets it slip that he "psychically" knows Lassiter is depressed because yesterday was a tough anniversary for him.
Walking down a hallway at the station, Shawn tells Gus they have to solve the case of the dead astronomer but make it look like Lassiter figured it all out on his own. Gus thinks it's dumb to solve a case and not take any credit -- or money -- for it, but Shawn tells him it's too late. He already has a meeting set up with the widow, in ten minutes. He's having her meet him in the chief's office, so he needs Gus to stand guard. Having the meeting like this is going to double the excitement -- maybe even triple it. Gus walks away, exasperated.
Shawn really does interview the astronomer's widow, Mary, in the chief's office, nervously keeping an eye Juliet, who eventually spots him. He gets the basics of the case from the widow, who stops him and asks whether his name really is Carlton Lassiter. Shawn says he is, but he is in no way affiliated with the other Carlton Lassiter whom she spoke with earlier. In fact, he spells his name with a K. Two of them. Shawn presses the widow for any info she may be leaving out. She admits she had suspected her husband of having an affair, but goes on to say she doesn't really think that. Her husband was a good man, and they were thinking of starting a family.
Shawn walks Mary out, and Juliet walks up to them. She demands, "May I speak to you privately in your office, K-Karlton?" Mary leaves, and Shawn comes clean to Juliet, telling her he wants to solve the case for Lassiter. She says she's in.
At the Psych office, Shawn tries to call his dad, but Henry isn't answering. Gus sees the case file and sarcastically asks Shawn if he found a partner who's willing to work on this case. Shawn says yes! Jules is in, his dad isn't answering, and hey -- that leaves Gus to step up! Gus is frustrated that he has to work two jobs while Shawn is out drinking and taking on free cases. Shawn finally tells Gus he'll want to take the case when he hears it's about astronomy. Shawn has been tailing Gus and discovered that he goes to the observatory every Thursday afternoon. Gus is annoyed that Shawn's been following him, but now that he knows Shawn's doing it, he tells Shawn he's going to be too quick and stealthy to be tailed from now on. He's going to be like a jackal.
Next scene, Gus sneaks off to the observatory (the caption telling us it's NOT Thursday), feeling good about having not been followed. He skulks into the building only to encounter Shawn, who now has a job there! After commercial, Shawn and Gus are walking through the observatory. Shawn wants Gus to interview the creepy lurking janitor while he grills the pretty intern girl. Gus says, "You are not grilling Jessica!" Shawn finally realizes that Gus isn't interested in astronomy; he's interested in Jessica. Shawn's ready to hook them up right now, but Gus has a lot of excuses about how he needs to have a plan, and needs to move gradually on a quality girl like her. Just then, she walks past. Shawn strikes up a conversation, trying to make Gus look good, and trying to get them to talk. Jessica can't chat; she has to start the planetarium show. Shawn volunteers to do it for her, and she agrees. She and Gus are left alone to get to know each other.
Back at the station, Juliet hands the astronomer's case file (the dead guy's name is Bryant Vallery) to a very mopey Lassiter. She takes all the info she and Shawn have gathered so far and talks to Lassiter as if he was the one who found it all out. Lassiter seems bewildered at first, but then perks up and makes a plan for running down the leads, saying, "I TOLD you there was more to this case!"
In the planetarium, Shawn is having a blast running the show and narrating with total nonsense. The creepy janitor guy comes in to help him. He stands too close, and Shawn sends him away. Then Shawn cranks some dials (not really having any idea what they do), sending the display into warp speed. While the audience gasps, he sneaks out to spy on the janitor, who steals some objects from a locker and walks off.
Shawn next visits the research room where the Bryant Vallery died. The other astronomer gets Shawn to help him align the telescope. Shawn strikes up a conversation about this seeming like a job for two people. The guy tells him he did have a partner, but he died not long ago. He tells him they only have the use of the telescope for eight months. He hasn't found what he was looking for yet, but he assures Shawn that he will, and it's big.
Gus and Jessica are walking and talking. They seem to be hitting it off, but as they walk up to the planetarium, she says, "They've been in there 45 minutes! It's a four-minute show!" Right on cue, Shawn leads the audience members -- dizzy and ill -- out of the planetarium.
Shawn and Gus compare notes. Shawn says the other astronomer is a nice guy, but definitely hiding something. He asks Gus how he did, and Gus produces Jessica's phone number from his pocket. They're going out tomorrow. Shawn says they have to meet Juliet at the station, since she has run Bryant's phone records. Gus is ready to go, but Shawn can't leave yet -- he has to finish his shift!
At the station, Lassiter is on the move, telling Juliet he's going to go talk to a cardiologist buddy of his about the dead guy's medical records, and Shawn and Gus walk in to talk with her about the phone records. There was one strange number that stood out on the records: 555-0199. Uh-oh -- that's Jessica's number.
Back at the observatory, Gus is upset that Jessica is a suspect. Shawn tries to tell him that they need to keep an open mind and not rule out any of their other suspects yet. Shawn is trying to get into the telescope room, but doesn't have a key. Vernon the creepy janitor arrives on the scene, but instead of busting them, he shows them how to break into the room. He doesn't have a key either; Bryant took it away after a few small items went missing from the room: a watch, a comb, some mail... Yes, he read the mail, and it turns out Bryant was a jerk. He was going to dissolve the partnership and claim total credit for whatever discovery they were making, and was apparently applying for some jobs he wasn't really qualified for, including a post at NASA. The three of them finally break into the telescope room. Vernon explains about all the books sitting around in the room: the partners used to switch off watching the sky and writing their observations in the books. He goes on about Bryant having become a jerk and Hugo being a nice guy -- Hugo even brings coffee for everyone every morning. Suddenly he tells them they should hurry; Hugo's here. No, he isn't psychic -- Hugo is just very consistent about coming to work at the same time every day. Vernon leaves. Shawn shows Gus that a page from the June 21 book is missing. Something must have happened between 8:39 and 10:42 on June 21. They leave the room, and run into Jessica on their way out. Gus thinks (hopes) Jessica may want to cancel the date, but she actually just wants to have it at 6:30 instead of their previously arranged time. Shawn helpfully chimes in so that Gus can't get a word in edgewise, because he still wants Gus to go on the date.
Hugo pulls up with the coffees and a locked briefcase. Shawn wonders why the observation readouts have to be locked up. Hugo goes in to do his work, and Shawn tells Gus they should search
At Hugo's house, they find some weird flowers growing -- in the vegetable garden, which is a little suspicious. They don't know what kind of flowers they are, but Henry is an avid gardener, so they'll bring one of the plants to him and ask him what it is.
Shawn wants to know why Henry hasn't been answering his phone lately. Henry puts him off, but just then a woman's voice is heard, asking where the towels are. Henry has a lady friend in the house! Her name is Sylvia. Would Shawn like to meet her? Shawn is a little horrified. He drops the purple flowers on Henry's porch and leaves abruptly.
At the station, Juliet is on the phone with Shawn, telling him she'll check out the June 21 lead, and goes on to say that Lassiter is on fire. Lassiter himself walks up and tells Juliet to get off the phone; he's on to something. He thinks Bryant was killed by someone he knew, and Bryant opened up a safe deposit box in June.
At Psych HQ, Shawn tries to get Gus to wear a wire on his date with Jessica, but Gus refuses. He also refuses to let Shawn follow him.
On the date, Gus gets Jessica to talk about her ex. She doesn't say who it was, but she tells him she found out he was married and broke it off. Gus seems relieved. Then she apologizes for having to move up their date, but she has to be at the observatory extra early tomorrow. She tells Gus it's top-secret, but Hugo and Bryant may have discovered an extra-solar planet. Just then, Shawn pops up from under a blanket on a park bench and exclaims that this is great news -- it means Jessica is no longer suspect! Jessica is upset, thinking that Gus was using her for information on the case. She stalks off, and Gus chases her.
At the observatory, Hugo is giving a press conference announcing that he found a planet. The reporters ask him about his partner. Hugo, a little agitated, says he did have a partner, but claims he (Hugo) is the one who made the discovery. Shawn's cell phone rings just then. It's Henry, wanting to know why he left a foxglove plant on his porch. Henry tells Shawn some neighbor cat could have wandered in, eaten the plant, and croaked right in his yard. Gus, overhearing the conversation, tells Shawn that foxglove has digitalis in its leaves. Shawn hangs up with Henry. Gus explains that digitalis is heart medicine, and given to someone who didn't have a heart condition, would be fatal. Lassiter and Juliet show up, and Shawn asks him about the poison. Lassiter can't remember having mentioned poison, although he does suspect it. Shawn offers to do a psychic reading for Lassiter to help him retrieve his subconscious thoughts on the case, and Lassiter humors him. Shawn tells him he wants to search Hugo's house; Lassiter concedes he is in the process of getting a warrant. Shawn goes on to say something dangerous is growing at the house. Lassiter tells him the problem is that the toxicology report didn't indicate any poison. Shawn cleverly gets Lassiter to "figure out" that the poison would have had to be administered very slowly over time. He asks Lassiter how one would accomplish that, and then exclaims, "coffee!" Lassiter (not getting it) says no thanks. Gus blurts "Tea! He was putting the digitalis in the tea every day for six months!" Gus is psyched he just solved the case, but Shawn and Juliet tell him no, Lassiter is the one who solved it. Lassiter, oblivious to this and quite willing to take the credit, orders Juliet to have the coroner look for digitalis, and get him a new pair of handcuffs -- he's back in the saddle! He arrests Hugo in the middle of the press conference.
At the station, Lassiter confronts Shawn about that night in the bar. Shawn admits that Lassiter mentioned his breakup with his wife. Lassiter goes on to say he thinks he had some help with this case -- but he's looking at Juliet, not Shawn, when he says this. Shawn reassures him that the truly great ones know when to accept assistance. Juliet walks up and tells Lassiter the press is ready for him outside. Lassiter walks off, confidence restored.
Shawn meets his Dad at the bar, and wants to know where Sylvia is. Henry tells him he didn't want to hurt Shawn's feelings, and asks him to sit down for a drink. Shawn wants to know if Henry's buying. Henry says, "Are you kidding?"