Watching Arcadia, the Tom Stoppard jigsaw puzzle currently playing at the Richmond Hill Barn Theatre, is like watching a really engrossing foreign-language film without subtitles. You may not understand what's going on, but the actors and director seem to, so you strive to make sense of the proceedings through the performers' inflections, reactions, and occasional lines of dialogue where the meaning is evident. You find yourself desperately wanting to get it.