"Chivalry Is Not Dead... But Someone Is" is the fourth episode of season five. A wealthy widow's young date is murdered, pitting Shawn and Gus against a dirty rotten scoundrel they are convinced trained the victim to be a con artist.
Shawn and Gus show up at a crime scene at a swanky mansion where a young bachelor, Lance, just fell to his death. Lassiter doesn't believe it was murder, but Shawn thinks otherwise. He notices that Lance's ankles and arms were not broken, causing him to think that he didn't try to brace his fall and was, therefore, dead before his body touched the ground.
They all head to Lance's bachelor pad to further investigate. Shawn spies a book called "Killing with Class" written by Clive Prescott, with a personal note from Clive. It turns out Lance was one Clive's most promising students in his "art of gentlemanly seduction" class.
An older woman, Gillian, whose husband recently committed suicide, was dating Lance at the time of his death. Lassiter and Juliet question Gillian. Lassiter thinks Gillian killed both her husband and Lance, and his theory is further validated when they spot Gillian dining with Clive Prescott.
Henry discovers that Prescott's most recent liaison was an extremely wealthy woman who went on vacation with Prescott in South America and mysteriously never returned with him. Shawn and Gus find Gillian and Prescott at the bank and interrupt a financial transaction the two appear to be making. Shawn charms Gillian and arranges a double date - Gillian being Shawn's date and Gillian's friend Eugenia being Gus's date.
At the date, Prescott crashes the party. Shortly after, the date then relocates to the Psych office, where it is hit again, this time by Lassiter and Juliet, who insist that Gillian is the killer. Shawn and Gus vehemently disagree, saying Prescott is the murderer. Suddenly, Shawn thinks he is poisoned and says that he thinks it was Prescott who has been behind this whole thing. At the hospital, Shawn finds out he was indeed poisoned, but barely. In fact, it turns out he's going to be just fine. Later, Shawn and Juliet question Prescott, but right in the middle Lassiter tells Prescott he is free to go, as they have no substantial evidence against him and can no longer detain him. Shawn and Gus disrupt Prescott's next seminar, calling him a murderer. Prescott makes excuses, but in the end, he sincerely declares his love for Gillian.
Privately, he tells Shawn and Gus that Gillian's friend Eugenia is practically penniless, and Gillian is her only caretaker. That's when Shawn puts it all together. Lance's friend Gabe was dating Eugenia. He broke up with her when he realized she had no money and poisoned Lance to get to Gillian. They go to find Gabe but instead find him dead in the sauna. Shawn then comes up with another theory. All the victims were lovers of Gillian's, leading Shawn to believe Eugenia killed them out of jealousy. Just as Prescott is going to drink a poisoned cup of tea, Shawn and Gus interrupt and save him. Shawn makes the claim that Eugenia is the murdering lesbian who was in love with Gillian. In the end, Eugenia admits to the murders, and Prescott leaves for his honeymoon with Gillian. As a kind gesture for his efforts, Prescott leaves Shawn in charge of his class.
As with so many Psych episodes, this one offers numerous nods to a classic 1980s comedy; here it's "Dirty Rotten Scoundrels", starring Steve Martin, Michael Caine and Glenne Headly.
The gallery for Chivalry Is Not Dead... But Someone Is can be found here.