As if the failure of his long-time marriage wasn't enough for Larry Gopnik (Tony-nominated Michael Stuhlbarg) to contend with, now his socially inept brother refuses to move out of the house as well. Larry is a modest man of science. Up to this point, his life has been uneventful at best, but things are about to get interesting. Informed by his wife, Judith, that she is leaving him to move in with his pompous colleague Sy Ableman, Larry does his best to contend with his failed marriage while doing his best to tolerate his unemployable brother, Arthur, who appears to have grown roots on Larry's couch. Meanwhile, Larry's son, Danny, is displaying a serious discipline problem at Hebrew school, and his daughter, Sarah, is stealthily snatching money from his wallet in hopes of saving up for a nose job. As Judith and Sy merrily begin making plans for their new life of domestic bliss together, Larry begins receiving a series of anonymous letters from a mysterious figure who seems intent on sabotaging his chance for tenure at the university. To complicate matters even further, a graduate student with failing grades is attempting to bribe the professor while simultaneously threatening to sue him for defamation. Larry is in some serious need of equilibrium, though it's hard to focus on getting your life in order when your beautiful neighbour insists on sunbathing in the nude just outside your window. Perhaps by seeking the advice of three trusted rabbis, Larry can finally learn to cope with his afflictions and finally become a genuine mensch.