The modern art world isn’t the best place to go to teach a lesson in morals, but Ten Unknowns gives it a whirl. In Ten Unknowns, Donald Sutherland plays an aging, almost-famous artist who lives in Mexico and refuses to show his new work. The big question is who’s painting it. Justin Kirk (Jack & Jill) is the brash assistant who has a mysterious hold over the old master, until a graduate student (ER‘s Julianna Margulies) stumbles into their world and affects the balance between them. Former boy wonder Jon Robin Baitz (The Substance of Fire) has written a sharp, intriguing first act, but his second act’s emotional explosions are forced. And it doesn’t help that his argument — which insists on a strict ethics of authorship — is muddled and naive. (Ironically, in his early work, Baitz seemed wiser than his years.) Margulies gives an amiable performance, but it’s Sutherland who really connects. At 6 foot 4, he’s a phenomenally physical presence, standing tall despite the drama’s shortfalls.