Watch The Hat Box Mystery for Free: How to Stream the Movie Online at 123Movies. . Susan Hart, assistant to private detective Russ Ashton, is given a camera concealed in a hat box and assigned to take a picture of a woman. A gun is accidentally hidden in the box and the woman is killed. Susan is charged with murder, but Russ and his less-than-useful associate, Harvard, get on the case and prove that the fatal shot was fired by the killer from across the street.