It starts off as a whodunit. And then the parallel storylines add to the mystique of what's going on and what's going to happen. However, as the plot unravels, it stretches.. And stretches your patience too. Until finally the movie ends with a whimper somewhat compared to the tautness that it carries till pretty much the last scene. There's a great deal of subtlety in the unraveling of the plot which doesn't work well, as it should have been less ambiguous. Even a Agatha Christie tale eventually makes sense of everything that had built the story up it until then. The acting is top notch, along with the period atmosphere that's been created.