Steve's (Robert Downey Jr.'s) ex-wife Mary (Catherine Keener) makes him realize that he can't really do anything about Nathaniel's (Jamie Foxx's) schizophrenia; that he should only "be his friend and show up"; this, after Steve and Nathaniel's last get-together ended up on a sour note, when Steve wanted Nathaniel to sign some papers to have him committed and Nathaniel, in response, snapped and told him that he despised him and didn't want to see him anymore.
Steve even convinces Nathaniel's sister Jennifer (Lisa Gay Hamilton) to come and see him; both she and Nathaniel meet at the LAMP Center, and reconnect and reconcile. Moreover, Nathaniel apologizes to Steve and they also make up.
A final sequence shows Nathaniel, Jennifer, Steve and Mary together, enjoying a classical music concert at Disney Hall -much to Nathaniel's pleasure, of course-, with the orchestra directed by Graham Claydon (Tom Hollander).
Title cards inform that Nathaniel was still sleeping inside -at his apartment, that is-, remained a member of LAMP and kept playing cello and a bunch of other instruments; Steve continued writing his column for the LA Times and was learning to play guitar; and that there are currently 90,000 homeless people on the streets of Great L.A. area.
A second epilogue is shown while the credits roll, with our main characters sharing a moment with the staff and members of the LAMP Center.