The Richmond Hill Barn Theatre's The Mousetrap is a reasonably entertaining presentation of author Agatha Christie's material. There were plenty of good laughs during Thursday's performance, and director Gary Clark and his cast did well in not giving away what's known as "the best kept secret in theatre" until its final reveal - that secret being the identity of a London murderer who is now, very likely, among the guests in the newly opened Monkswell Manor boarding house.