A Masculine EndingMovie

While English professor Loretta Lawson is attending a conference in Paris, she stays the night in the flat of a friend's acquaintance. She discovers a sleeping man in one of the bedrooms, and the next morning finds the man gone, but the bed soaked with blood. Returning to Cambridge, she begins to suspect her friend's acquaintance, and others on the staff of the college, are involved with the missing (murdered?) man, and decides to investigate for herself.