Continuity mistake: When Mrs. Maxwell, the head of the "Occult Society", is arguing with her husband Milo, watch her dish of tapioca. In the first shot, a profile shot, the dish is full. When the shot switches to a head-on shot, the dish is nearly empty. In the next profile shot, the dish is once again full and she's just then taking her first bite.
Revealing mistake: After Luther faints from seeing the shears in the painting of Mrs. Simmons, the beam of light from his flashlight continues to move side to side, but Luther's flashlight is in his hand, unmoving.
Continuity mistake: After Luther slides down the coal chute and into the coal bin, his left arm is outstretched, but the next shot of Luther shows his left arm immediately beside him.