Other than Rose Byrne’s on-screen radiance and a soothingly warm palette lit by cinematographer Seamus Tierney, there’s not much to get passionate about in this amiable chamber piece from theater director Max Mayer. Hedging just about every bet it lays on the table to the tune of a gentle guitar, Adam spins a wish-fulfilling romance between a recently bereaved young man with Asperger’s syndrome (Hugh Dancy) and his beauteous new neighbor, Beth (Byrne), who all too conveniently happens to work in a helping profession. Writer-director Mayer tries to reduce the improbability quotient by loading Beth up with burdens of her own (including Peter Gallagher, who does “feckless father” in his sleep) that test the authenticity of her values. To his credit, Dancy doesn’t take the showstopping Rain Man route, but, however underplayed, his Adam is all too authentic for most social intercourse. Clogged to the pore with pathos (boxes of mac-and-cheese stacked in Adam’s freezer), bogus romanticism about mental illness (Adam sees natural wonders the rest of us don’t), the obligatory kindly black helper (Frankie Faison), and the saintly patience of the love interest, Adam only confronts reality at the end, when it timidly owns up to the likelihood that such relationships only work if the healthy partner is willing to become a mother, not a wife.