Saw movie scene on tv in early 60s 9possibly late 50s). It as black and white. It was a mystery set in a large building (in the scene i saw). Seems british in my mind, but could be usa. Movie probably from 30s or 40s. Bunch of well dressed people in a large house/mansion. Obviously a mystery. Much discussion then move to a cave to explore (looking for evidence i think). One character, a man, notices a chain on ground. Movie shows chain being drug away, but not who pulls it. Man later notices chain is gone. tells no one. I get called to dinner and never see any more of the movie. H!as bugged me ever since.