Continuity: Roger St. Luc rings the old Québequois couple from the lobby after being attacked in the basement. In the previous scene, however, the viewer sees the manager cut the phone lines. Despite this, the French couple answers the phone and tell St. Luc that his girlfriend, the nurse, has left the apartment. But the reason that she left the apartment was because the phone had been cut off.
Revealing mistakes: In the theatrical version, the viewer can see the wire that moves the parasite in the very first shot it appears in (in the garden, after it fell on the old woman's umbrella). However, the wire is so thin that it is invisible in all home video editions.