Deliberate "mistake": After the killer nails Shannon to the ceiling, he apparently has time to remove all the nails from the wall where he originally shot her, spackle, paint and clean up all the blood before the police arrive and examine the apartment.

Continuity: When Austin's mum tells him not to stay up too late, he deals the cards in his computer game of solitaire twice between shots.

Continuity: When Nell is flipping through the magazine Charles gave her, she finds a note inside the magazine. It then cuts to a side shot and you can see the pages she had the magazine open on are different.

Continuity: Nell writes a note to Julia after she misses their morning run. Between shots the handwriting of the note changes - the letters are different in spacing and size.

Continuity: Austin unknowingly recorded Julia's death through her webcam. However, what he sees on the recorded copy is not how it happened when we originally see Julia killed. The way she is thrown to the bed, the green curtains, and the amount of time spent wrestling the killer are all different in the recorded copy.

Continuity: The mannequin by Daisy's door has a yellow hat on it, but later when she runs to close the front door, before the murderer jumps out, the yellow hat has vanished.

Continuity: When Austin's mum walks in on him watching Julia on webcam, he quickly opens up a solitaire programme. Between shots the cards on the screen are constantly changing without him touching anything.

Continuity: When Daisy stands by the elevator, buckling her umbrella back up, the position of the umbrella in her hands changes between shots.

Continuity: When Nell is out on the balcony, where the rocking chair is, the angle at which the door is opened changes in every shot.

Continuity: When the killer decapitates Ned, you can see from the body that the head was severed at the neck, but when he drops Ned's head on the floor; it's severed just below the eyes.

Continuity: Nell is sorting clothes into a laundry basket, when she hears fighting next door. She goes to listen through the wall, then goes back, only now the positions of clothes in the basket has changed.

Continuity: In the laundry room, when Nell is talking to Charles, a box of washing powder appears on the washing machine between shots.