Ustinov, BathIn an emphatic production that prowls around the mess of human motive, Peake's Sister Aloysius doggedly pursues a suspicion of abuse John Patrick Shanley's play first appeared in 2004, the era of known unknowns. His parable about a priest suspected of abuse was, he has said, partly prompted by the search for weapons of mass destruction in Iraq: war justified by unproven conviction. He depicts a 1960s Bro…