Effectively portraying an emotionally shut-down middle-aged man who's squarer than a block of wood is difficult enough; but to do it in a musical — about spree-killer Charlie Starkweather no less — requires an exceptional combination of talent and technique. Zachary Allen Farmer met both requirements in spades. His eyes hidden behind bulky glasses, Farmer conveyed Sheriff Merle Karnopp's repressed inner life through a deadpan mouth, muted movements and a glowering presence. Then the dam broke, and Farmer's rich voice flooded the room with "Someday," and all the smothered tenderness of Merle Karnopp manifested; every strangled movement and slowly bitten word that followed illuminated the emotional damage wrought by a lifetime of repression. In this New Line Theatre production, Zachary Allen Farmer drew a portrait of the man in negative, every shadow and snarl a window into a lonely, hurting soul, as wounded as Charlie Starkweather himself but better able to hide it.