Commercial jingle writer Charlie Harper (series star Charlie Sheen) is a wealthy bachelor with a house at the beach, a Jaguar in the garage and an easy way with women. But his Malibu lifestyle is interrupted when his uptight chiropractor brother, Alan (series star Jon Cryer), arrives unexpectedly with Alan's 10-year-old son, Jake (series star Angus T. Jones). Alan's wife, Judith (series star Marin Hinkle), suspecting that she may be gay, wants a divorce. Charlie reluctantly allows Alan and Jake to live with him temporarily, but as it becomes increasingly obvious that Judith is never going to relent, Charlie and Alan's self-obsessed, controlling unmarried mother, Evelyn (series star Holland Taylor), offers to let father and son live with her. However, by that time, Charlie has formed a close bond with the clever Jake, even learning a few things about poker from the boy. Charlie also finds out that pretending to be a single dad with a cute kid can be a great lure for women. Meanwhile, Charlie tries to evade Rose (series star MelanieE Lynskey), an attractive, offbeat neighbor who had a brief fling with him and remains determined to stay in his life by whatever means necessary. Missing Jake, Charlie surprises even himself and asks Alan and Jake to live with him permanently. Despite their strained relationship, the brothers discover that they have one thing in common: They both love Jake and want what's best for him. Together these two-and-a-half men face the challenges of growing up.

Unsure how to properly discipline Jake, Charlie ignores him after the child "forgets" to stop feeding the seagulls and leaves the door open. As a result, the gaggle of birds enters the house. Meanwhile, Alan gets a surprise from Judith when he goes home to fix her sprinklers.

When Alan's attempt to provide Jake with a fun-filled father/son weekend backfires, Charlie tries to console his brother by taking him to a local bar and getting Alan totally inebriated. As Alan and Charlie travel home, their meddling Cab Driver (DARRYL SIVAD), hearing the brothers' woes about their narcissistic, controlling mother, offers them some unsolicited therapy.

Charlie's longtime cleaning lady, Berta (recurring guest star CONCHATA FERRELL), quits her job, and Charlie quickly realizes he can't function without her. When Alan tries to take Berta's place but doesn't succeed, Charlie sends him to lure her back. Meanwhile, Alan places Charlie in charge of getting Jake ready for Judith, who is coming to take her son out for a nice dinner with her parents. Rock star STEVEN TYLER of the band Aerosmith does a voice-over as himself.

After a drunken night in Las Vegas, Charlie reluctantly attends one of Jake's soccer games. But Alan and Charlie soon discover the advantages of going to these matches. The players' mothers are quite attractive, and Charlie makes a date with a particularly sexy soccer mom. Meanwhile, when two single mothers discover that Alan is newly available, they "hit" on him--literally.

Charlie rethinks the way he treats women when he, Alan and Jake are forced to cheer up a pitiful Evelyn after her serious new boyfriend terminates their relationship. Meanwhile, Charlie teaches Jake some valuable lessons about screening calls from women, but the lesson backfires when Jake reveals a little too much about what he's learned to a disapproving Alan.