Charlie Sheen is "Charlie," a successful therapist who thrives on the chaos in his life while still battling his own anger issues. Charlie's colorful cast of patients includes his weekly regulars and the group of inmates he counsels pro bono at a state prison. His life is further complicated by his relationships with women, including his own therapist and best friend (Selma Blair), his ex- wife (Shawnee Smith) and his 13-year-old daughter (Daniela Bobadilla).
When Charlie almost beats his ex-wife's boyfriend with a lamp after an anger relapse, he decides he needs to go back to therapy. Unfortunately, he is currently having sex with the only therapist he trusts: his best friend Kate. Since the number-one rule of therapy is not to have sexual relations with patients, Charlie must choose between his love of sex and his need for help.
Charlie is visited by a troubled woman he had a one-night stand with while playing in the minor leagues. Wracked with the guilt of using her as his "slumpbuster", he pretends to date her and realizes she acts like less of a girlfriend and more of an obsessed stalker.
Charlie challenges his group to do thirty-six hours of sleep deprivation therapy so that their "inhibitions come down and the truth comes out" - except the result turns out to be the exact opposite.
A long-standing rivalry over who's a better therapist leads to war when Kate steals Patrick, one of Charlie's group patients.
Charlie falls for Jen's hot new business partner, Lori - played by Charlie's real-life ex, Denise Richards - only to find she thinks therapy is a scam. In the therapy group, Patrick asks Charlie to counsel the angry ghost of his mother, who he believes is haunting his apartment.
Inflamed by Kate's comment that he's only "nouveau smart", Charlie starts covertly dating a brilliant coffee-shop barista. The only problem is that the woman is turned on by sex where there's a chance of getting caught -- and she's Kate's patient.
Charlie and his ex, Jennifer, are having an issue with how Charlie still tries to manage her life when Cleo - one of Charlie's patients from his prison anger therapy group - shows up on his doorstep, fresh out on parole. Jennifer decides to get back at Charlie by dating the ex-con.
Charlie has to evaluate the depth of his involvement in his patient's lives when he accidentally helps his patient who vicariously enjoys other people's anger hook up with a crazy woman.
Charlie gets an unexpected visit from his hyper-critical, bullying father - played by Charlie's real-life dad, Martin Sheen. In the therapy group, Charlie attempts to help Lacey with road rage.
After Charlie and Kate have sex, he innocently asks her if she wants to go to a movie. Kate interprets this as a romantic gesture, rushes to fix him up on a date the next day with someone else and the two are forced to exam the nature of their odd relationship. At home, Sam kisses a girl at school and a picture of it ends up on Facebook.