Goofs

When Vance and fellow detectives investigate the body of Robin, who has been shot with an arrow, the angle of the arrow changes. Sometimes it's straight up out of the body, other times it's at almost a 45 degree angle.

Zelda Sears is credited on-screen as playing "Mrs. Otto Drukker", but throughout the film she is called Miss Drukker and is referred to as the sister of Adolph Drukker, with no other Drukker in evidence (in particular, there is no Otto). This does, however, duplicate the name given in the "Cast of Characters" of the original book by S.S. Van Dine. (Although, in the book, she is listed as Adolph Drukker's mother.)

When Philo interviews Ms. Drukker, she's lying on a sofa, with her right side against the back of it. But when a shot shows her reflection in a mirror, her right side is still up against the back, while her left side is exposed, when it should be the other way around.