Alan Johnson (DON CHEADLE) is a dentist with a thriving practice, an attractive wife in Janeane (JADA PINKETT SMITH), and two adorable girls. Yet, he isn't completely happy, not only because he's uneasy about a beautiful patient, Donna Remar (SAFFRON BURROWS), repeatedly coming on to him, but also because Janeane wears the pants in their family, a point he brings up with psychiatrist Angela Oakhurst (LIV TYLER).
Things change when he runs into his former college roommate, Charlie Fineman (ADAM SANDLER), a one-time dentist who gave up his practice and most everything else following the death of his wife and three girls in the terrorist attacks of 9/11. Unable to deal with his grief or the attempts of his in-laws, Jonathan (ROBERT KLEIN) and Ginger Timpleman (MELINDA DILLON) to contact him, Charlie's only social contacts are with his landlady, as well as his former friend turned personal lawyer, Bryan Sugarman (MIKE BINDER), who now watches over Charlie's insurance and government payout funds.
Feeling sorry for his former friend, Alan hangs out with Charlie, playing video games in his apartment and zipping around the city on his motor scooter. His new late-night activities, however, don't sit well with Janeane, putting even more of a strain on their marriage. Yet, Alan is committed to help make Charlie better, and thus tries to do just that, including through Angela and other means.