Gus' Uncle Burton is in town for a visit, and since Gus has spent all his life trying to live up to his namesake's expectations, he does not correct him when he mistakenly hears that it's Gus who is the psychic detective, for fear of disappointing him yet again. That means that when Uncle Burton tags along on their investigation into the death of Vince Wagner, a prominent restaurant critic, Shawn must help Gus find clues while Gus pretends to be psychic. Shawn looks around and sees leftover containers and evidence of bad cooking. He leads Gus to a "vision," quickly disregarding the wife as a suspect. She was a bad cook, but she was trying to get her husband to eat healthy, not kill him.
On the way out, Shawn sees that the critic's tongue was stained black. Gus tells him it was probably a side effect of stomach medication. Shawn's now sure he was murdered, but not by the wife. He was complaining of a stomachache before he ate her food. Shawn then leads Gus to explain to his uncle that the spirits told him Wagner was poisoned by some food he ate at a restaurant. With Uncle Burton in tow, they go to the police station, where Gus tells them about their suspicions of murder, possibly by a chef who was unhappy with a bad review. Interim Chief Vick says they will run a tox screen and double check.
Shawn then figures that the poison probably came from the last restaurant he visited and remembering the take out container at Wagner's house, they head to Antonio's to check it out. Explaining they are there for a surprise health inspection, Chef Antonio is taken aback, saying he just had a surprise inspection a few days ago, but shows them around regardless. As he is telling them that he hated Wagner for always giving him bad reviews, Lassiter and Juliet arrive to arrest him, telling Shawn and Gus that there were poisonous Death Cap mushrooms in the risotto he served Wagner. As they take the chef away, Shawn notices that the mushrooms at the restaurant are cut differently than the ones in the take out container at Wagner's house. They've got the wrong guy.
From Wagner's notebook, they see that his mushroom risotto was served cold, something Antonio would never do. That risotto was prepared somewhere else. They need to see if Wagner had any other enemies. They go to his newspaper office and after getting rebuffed by the editor, Phil Pritkin and his assistant, Nick, they speak with Wagner's assistant, Cooper, who shows them Wagner's extensive file of hate mail. They decide to start with questioning the chefs whose letters contained death threats but the only things they learn is that all of them have alibis and that Wagner led the good life, eating free gourmet meals every day. A life so good, in fact, someone might kill to get it. Maybe, someone at the paper. In order to do some serious snooping there, Shawn gets hired as the new astrological forecaster which gives him access to the applications for the critic's job, a job Phil tells them everyone wants, including Nick, who proceeds to give an impromptu review of the Cheetos he always eats. Now they just need to match one of the applicants to the murder weapon. For that they visit the only mushroom farmer around, who tells them that someone was there recently asking about the Death Cap mushroom. But the farmer seems less than reliable, telling Shawn and Gus that the man they're looking for is nine feet tall with sunshine coming out of his mouth and a hippopotamus for a hand.
Back at the Psych office, they find Henry who tells them that Chef Antonio at one point put beef broth in his vegetarian burgers to add flavor. A vegan activist named Dwyer found out and has had it in for Antonio ever since. Maybe Dwyer framed Antonio for Wagner's death to put him out of business. Henry tells them she'll be easy to find, she's been chained in protest to a fast food restaurant for three days. When they talk to her, she admits she was at Antonio's the same night as Wagner but is cleared when they find out a homeless man died of discarded Death Caps downtown the day before. Her alibi is a lock. Plus, the description of the suspect is a six-foot tall man. Shawn and Gus find out that the dumpster is near the newspaper. They were on the right track in the first place. But before they can go down there, they have to rush Uncle Burton to the airport, who complains that with all the running around he forgot to pack his new shirt with the hippo on the sleeve. Shawn then finally deciphers the muddled description of the killer they got from the mushroom farmer and rush back to the paper. With the cops and Uncle Burton there, Shawn and Gus must deconstruct the crime together, explaining that Antonio's first surprise inspection was actually Nick, sneaking in the homemade spiked risotto. Nick, who wears the hippo shirts and is always eating Cheetos, giving his mouth a sunshine like glow. With the case solved and Gus looking like a hero, Uncle Burton goes home finally giving his nephew the approval that has been so long sought.