Plot hole: When Jack The Ripper checks his watch before confronting H.G. Wells and demanding the key, the hands point to 8:50, the ensuing chase to the museum and demise of the Ripper may have used up a half hour or so, yet the time on the wall clock indicates that it is midnight.

Continuity: In the scene where Mary Steenbergen and Malcolm MacDowell are in a restaurant and he's eating ice cream, his hand holding the ice cream spoon is in a different position when he's shown from the front than from when he's shown from the back - one way it's up, the other it's down. Also, the spoon disappears whenever the shot is from the back.