Recently I read about a private investigator in the US who would knock on a door, show his badge to whoever answered, and say, “I guess we don’t have to tell you why we’re here.” Many times, the person would look stunned and say, “How did you find out?” then go on to describe an undiscovered criminal act committed long ago. Writing in Smithsonian magazine, Ron Rosenbaum described the reaction as “an opening for the primal force of conscience, the telltale heart’s internal monologue.”