Continuity mistake: In the dining room, Mary places the telephone on the kitchen counter by reaching through the double doors over the bar. The doors, which she pulls shut, bounce back open slightly on their own. Mary then commits suicide. No one else has been there, but when Agatha returns to discover the body, the bar doors are tightly shut again. (00:35:10)
Continuity mistake: During his questioning inside the house, Clemens' hair goes back and forth from falling over his forehead to brushed back several times between takes. (00:05:00)