Revealing mistake: During Ian's double-kill moment in the morgue, you can see the prosthetics on his chest crease once he drops to his knees for the fatal blows. (01:14:00)
Continuity mistake: The size of the knife wielded by the girl during the junkie Ian scenes changes significantly from a large butcher knife in the kitchen, to a small steak knife once outside when stabbing the evil girl. (00:45:30)
Plot hole: After the first death, Ian is in the office and after the conversation with the girl the scene starts to speed up, indicating that time is passing by at a fast pace; yet even with the rapid time change, the sun's rays that pass through the office never move or change in any way as it should.
Continuity mistake: Standing in the subway talking about what the creatures were, the blood from the infected tract wound from the heroin needles is completely gone, as well as the entire wound itself. (00:46:30)