Any actor on the fast track to stardom who chooses to play a sexually ambiguous character can be said to have made a daring choice. In A Home at the End of the World, based on an acclaimed novel Michael Cunningham wrote before ''The Hours,'' Colin Farrell makes that and other bold choices as well. As Bobby, a wonderstruck 24-year-old virgin who grew up idolizing his acidhead older brother, he's playing a dazed, tremulous, utterly openhearted young man: the last flower child in America.
Most of the film takes place in the '80s, and for a while, as Bobby moves to the vibrant squalor of New York's East Village, Farrell wears a shaggy hippie wig that has the unfortunate effect of making him look like Treat Williams in Hair. Even after Bobby's locks are shorn, though, it's nearly as disquieting to see the actor use his brusque sensual features -- the raffish grin, the eyebrows that slope like greasepaint slashes -- to express the gawky innocence of a polymorphously sweet man-child. Farrell does all that he can to act guileless, yet you can tell how hard he's working. He still stalks around with the wiry ease of a born stud, making his vulnerability seem like an act.
Bobby has come to New York to visit his childhood best friend, Jonathan (Dallas Roberts), only to be drawn into a complicated emotional and erotic triangle. The two shared a few furtive liaisons as teenagers, and Jonathan, who is still in love with Bobby, now cruises for one-night stands. His roommate, Clare (Robin Wright Penn), a scraggly bohemian hatmaker, falls for Bobby too, and seduces him, yet the situation could hardly be less sordid. Bobby serves these two as a spiritual boy toy, and it's the conceit of the film that the three forge a new kind of family. They even move to the country and have a baby!
If you thought that ''The Hours'' conveyed more thematic grandeur than it did dramatic sense, just wait until you see ''A Home at the End of the World.'' It has moments of fine acting, notably from Dallas Roberts, who gives Jonathan a witty, coiled decency, yet the first-time director, Michael Mayer, never begins to ground these unorthodox relationships in the bedrock of dailiness. Most of the movie feels like Farrell's performance: deeply sincere, and more showy than convincing.