Harold Pinter plays are often oblique, brutal, and savagely funny affairs. They are also notoriously difficult to stage, as the Nobel Prize-winning playwright leaves nearly as much out of the dialogue as in. Actors are pushed hard, but the results can be absolutely bracing. The six performers in The Birthday Party at the Jungle Theater — Stephen Cartmell, Claudia Wilkens, Richard Ooms, Tony Papenfuss, Martin Ruben, and Katie Guentzel — spun the material into a fine evening at the theater. While Cartmell may have been the hero — well, victim really — the rest of the cast carved out their territory as well: Wilkens and Ooms's elderly homeowners, Papenfuss and Ruben's mysterious strangers, and Guentzel's not-what-she-seems innocent girl next door. While they found their own spaces, the actors also melded as a company, which becomes more and more important as the play deepens and darkens along the way. Pinter's play came to life in a way rarely seen on area stages, and much of that was due to the talents and efforts of the six actors.