British comic and sometime transvestite Eddie Izzard makes a serious impression in this smart revival of Peter Nichols' 1967 play. Izzard plays Bri, the father of a deeply autistic child -- ''a wegetable'' as he puts it -- who covers his despair with wall-to-wall humor. At first, you might find yourself fighting the laughter -- given the abject presence of the child -- but Izzard is uproarious and unstoppable, especially during a major digression in which he and his excellent costar Victoria Hamilton break the fourth wall to recount their parental history. This lengthy sequence gives Izzard the opportunity to play several characters (including a thickly accented German doctor and an ineffectual priest) through which he infuses laughs with an anxiety-producing backbeat, much in the manner of Peter Sellers. Disappointingly, the play's final twists lack dramatic inevitability. We're supposed to believe that Bri has lost all hope, but Izzard is such a joyous performer we really don't buy it.