Possibly a British film made in the late thirties or early to mid forties. Involves a closed up room. Someone (possibly the heroine) climbs up the outside of the hourse, and enters the room through a window. Turns out a couple of servants at the estate are trying to gaslight the young man into believing he is a murderer. He lets them leave the house, but they have to pick one of two paths through the moors. One path leads to safety, the other to quicksand (?). Of course, being evil, they pick the wrong path and perish in terror. Very atmospheric film.