Chris McGarry plays Father Flynn, the priest under suspicion for abusing children in “Doubt,” John Patrick Shanley’s brilliant play at National Theatre.

“From an actor’s point of view, I’m impressed by how beautifully Shanley maintains ambiguity,” McGarry says. “For my part, I try to be as neutral as possible, not too guilty, not too innocent. Only the playwright, director and I know what really happened. None of the others know.”