Charlie's new girlfriend grows frustrated with Rose, who continues to stalk Charlie.
Charlie and Alan plays matchmaker for Evelyn and try to set her up with Russell (Martin Mull), the pharmacist.
Tempers flare when Walden, Alan, Lyndsey and Zoey are trapped in the house during a storm for a sequestration that might result in another Valentine's Day massacre.
Walden pleads with Kate to give their romance another shot when he's lonely on Valentine's Day. Meanwhile, Alan's holiday with Lyndsey doesn't proceed as he'd hoped.
Soon-to-be father Peter Highman goes on a wacky, cross-country road trip with quirky misfit Ethan Tremblay in order to attend the birth of his child.
Berta takes a few days off and Charlie falls for the woman who replaces her.
Charlie spends money wildly for his old lover Courtney, who returns after spending three years in prison.
Alan gets creative with a gift for Lyndsey when he's ashamed that he can't afford an expensive present.
Charlie and Courtney split up, and a depressed Charlie seeks solace from his psychiatrist, Dr. Freeman.
Alan becomes paranoid when Charlie and Lyndsey start to become friends.
Charlie can't get over Rose being married, and he begins to stalk her; and Alan is worried when Jake and Eldridge make videos of each other performing dangerous stunts.
Charlie and Rose's affair continues while Alan's chiropractic business turns shady.
Alan learns Rose's secret when he meets her "husband," and Rose uncovers Alan's Ponzi scheme. Meanwhile, Charlie scrambles to find time to be alone with Rose.
In Part 1 of a two-part ninth-season opener, Ashton Kutcher joins the cast as brokenhearted billionaire Walden Schmidt.
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