Charlie Harper (series star CHARLIE SHEEN) is a well-to-do bachelor with a house at the beach, a Mercedes in the garage and an easy way with women. His casual Malibu lifestyle was interrupted when his tightly wound brother, Alan (series star JON CRYER), and Alan's young son, Jake (series star ANGUS T. JONES), came to stay with him a couple of years ago.
When Jake's school principal demands to meet immediately with Alan concerning a picture Jake drew of a large-breasted schoolmate, Alan leaves a phone message asking Charlie to help, but Charlie doesn't respond.
Charlie is dismayed to learn that Alan's recent dating spree has been with Alan's ex-wife, Judith. Charlie fears he will rarely get to see Jake if Alan and Judith reconcile. So Charlie does everything in his power--including trying to distract Alan with beautiful women (Former Playboy Playmates SANDY and MANDY BENTLEY)--to keep the two apart.
Alan infuriates Charlie when he gives Berta permission to move into the beach house for a couple of days. Charlie reprimands Alan and informs him that he's just a houseguest and doesn't have the right to allow Berta to stay with them. Hurt by Charlie's reaction, Alan decides that he and Jake need to move into their own place.
After a woman Charlie has been having sex with professes her love for him, he responds inappropriately and suffers from impotence. Later, Rose explains that Charlie's inability to have a long-lasting relationship is due to unresolved issues with his mother.
Charlie is thrilled that he's dating Isabella (JODI LYN O'KEEFE - "Nash Bridges"), a wild, sexually uninhibited woman--until Alan points out that she's a spooky Satan worshiper. Charlie is unfazed by Alan's warnings until Isabella threatens to put a curse on his manhood.
Charlie finds himself in a compromising position after getting drunk and spending the evening with his stalker, Rose, celebrating her birthday. He ends up being confronted by her father, Harvey (Golden Globe and Emmy Award winner MARTIN SHEEN - "The West Wing"), who demands to know Charlie's intentions towards Rose.
After Charlie's romantic overtures towards Mia (recurring guest star EMMANUEL VAUGIER - "Smallville," "One Tree Hill," "Saw II"), an attractive ballet teacher, are rejected, Charlie tries to prove to Alan that he can persuade Mia to go on a date with him.
A wealthy, elderly woman named Norma (Academy Award and multiple Emmy Award winner CLORIS LEACHMAN - "Malcolm in the Middle," "Spanglish") is romantically interested in Alan.
Alan organizes a family dinner to celebrate the publication of a newspaper article that describes him as a "good doctor, good neighbor and a good guy," but he's crushed when his mother, Evelyn, isn't impressed.
When Alan dates a cooking instructor, Sandy (JOSIE DAVIS - "Beverly Hills 90210"), both he and Charlie gain weight. But even as it becomes clear that Sandy is mentally unstable, Charlie refuses to allow Alan to break up with her, fearing the loss of her fabulous meals.
Charlie and Alan take Jake to a friend's house and go out for some sibling bonding at the movies, but their night is ruined when Alan freaks out after convincing himself that Jake was too eager to spend the weekend away from him.
No one believes Charlie when he says that his relationship with Mia (recurring guest star EMMANUELLE VAUGIER) is getting serious, and everyone really thinks he's lying when he confesses that he and Mia have been dating for more than a month and haven't consummated the relationship.
After a month and a half of abstinence, Charlie is quite eager to consummate his relationship with Mia (recurring guest star EMMANUELLE VAUGIER). Unfortunately, there are still a few roadblocks, including Charlie's oversexed ex-girlfriend, Kandi (recurring guest star APRIL BOWLBY), and Mia's parents.
Charlie's lifestyle causes tension with Mia (recurring guest star EMMANUELLE VAUGIER). Charlie can't keep pace with the healthy routine that Mia has introduced into their relationship, so he sneaks cigars and beers in the garage and enlists Rose to deliver burgers to him on the sly.
Concerned that he is dating a woman half his age--and mortified to introduce her to Evelyn--Alan tries to avoid bringing his sexy 22-year-old girlfriend, Kandi (recurring guest star APRIL BOWLBY), to Jake's birthday party. Meanwhile, Rose continues her passive-aggressive pursuit of Charlie.
When he is nominated for an advertising award, Charlie boycotts the banquet, having lost several years in a row to his cocky competitor, Archie (JON LOVITZ - "Saturday Night Live," "Happiness"). After devising a ploy to get him to attend, Alan, Evelyn and Jake accompany Charlie for support--but then they get to know Archie.
Alan gets into financial trouble because he keeps paying the expenses of his young girlfriend, Kandi (recurring guest star APRIL BOWLBY). When Kandi's old car breaks down, Alan leases a new one for her. Charlie warns him to break up with her, but Alan spends his last dime on Kandi's root canal and can't pay alimony to Judith, forcing Charlie to cover for him.
Kandi (recurring guest star APRIL BOWLBY) moves in with Alan and Charlie, causing tension in the house. Charlie's not happy to learn of the new arrangement, considering he himself has been having a dry spell with women. Things begin to look up for Charlie, however, when Judith befriends Kandi, and a special visitor comes knocking on his door.
Charlie is now dating Kandi's (recurring guest star APRIL BOWLBY) mother, Mandi (recurring guest star GAIL O'GRADY). Meanwhile, Alan is depressed because Kandi has left him and is staying with bitter Judith, who brainwashed her against him. At Mandi's urging, Alan goes to Judith's place to try to win Kandi back.
Jake's teacher, Francine (JULIA CAMPBELL), calls Alan and Judith into her classroom to discuss Jake's lack of interest in school. Desperate to communicate with someone intelligent while continuing to see his airhead girlfriend, Kandi (recurring guest star APRIL BOWLBY), Alan falls for Francine--in a platonic way.
When a cute girl from Jake's school invites Jake to a party, Charlie butts in on Alan's milestone moment with his son by offering his own words of wisdom on women. While Alan feels somewhat jealous that Charlie is taking over, he realizes he also feels envious that his son is receiving some solid advice on scoring with women that he wishes his brother had taught him.
When Charlie finds out that his ex-girlfriend, Mia (recurring guest star EMMANUELLE VAUGIER), is in town with her dance troupe and wants him to come to her performance, he opts not to go and tries to behave as if he were no longer attracted to her.
With Charlie and Mia (recurring guest star EMMANUELLE VAUGIER) arranging their wedding, their families meet, and things immediately begin to fall apart. Rose takes Charlie's engagement news hard and makes some interesting plans of her own. There is also the question of where Alan and Jake will live after Charlie and Mia get married.