He sleazed his way into homes across the country as Scott Templeton on the electrifying fifth and final season of HBO’s “The Wire.” He changed the face of independent American cinema with his homespun tale of relationships lost and found in The Station Agent. And now, with The Visitor, writer-director Tom McCarthy is crossing the border into mainstream film. Sort of. As one might well guess, it’s a trip.

"Care for a moss ball?" asks Tom McCarthy, smiling, as he waves me over to the nearby couch in his suite at Manhattan's Regency hotel. He lobs the stupid sphere back and forth between hands, contemplating its absurdity, before tossing it back into a display bowl. The affable writer-director-actor is here to promote The Visitor, his return to the director's chair after 2003's critical treasure The Station Agent. To suggest that McCarthy's latest film is a near-perfect exploration of friendship and diversity would be saying too little. It stars Richard Jenkins of "Six Feet Under" fame as Walter Vale, an economics professor whose reticent malaise has eclipsed his passion for life. When coerced into speaking at a conference in New York, Vale packs his bags and returns to the Manhattan apartment he left years earlier. But there are now two illegal immigrants living in his place. What should then devolve into a logistical nightmare somehow blossoms, through music, into a series of unlikely friendships. A decidedly tragic film, The Visitor explores the lifelessly sanitized purgatory of immigration detention centers across America. It's also heartwarming at times, funny at others—which seems appropriate, given that its director, who is here to talk about his passion, can't seem to get his mind off those damn balls.