Continuity mistake: Riley puts the red hard-covered book and two others into the box, but puts the same books into the box when Gabby starts to help. (00:13:35)
Continuity mistake: At the double murder scene, the commissioner asks the eyewitness about the van. In the background, a policeman opens the trunk of the car, fully. He is back in the process of opening it in the next shot. (00:44:15)
Factual error: Rose's legs were paralyzed, but when she was dragging herself on the floor, she occasionally used her feet to help propel her body forward (and moved her feet downward) - something she would not be able to do if her legs were paralyzed. (00:33:40)
Continuity mistake: Leonard washed his hands and some of the blood on his shirt cuffs/sleeves got wet and diluted, but his cuffs/sleeves were dry when he walked out of the room. (00:28:40 - 00:29:05)
Revealing mistake: Luke points a flashlight along the side of the staircase, but no shadows are produced on the wall from the vertical posts. Luke points the flashlight in front of himself and produces his shadow on the wall behind (and the shadow doesn't look like the way he is holding the flashlight). After Luke goes through the entryway aiming his flashlight ahead, a circle of light is behind him. The power is out, so the flashlight is the only light source - except that used for filming in the dark. (01:03:00 - 01:05:25)
Factual error: Doctor Key tells Mary, "If you pose a threat to those around you, we will be forced to keep you here [hospital] longer. That means your son will be placed in foster care." Family members, such as the grandmother and uncle currently taking care of Tony, are preferred before placement in foster care. Foster care is usually considered among the last resorts, not first, and only when there are no suitable family members or significant others to provide temporary care for a minor. [SPOILER: It isn't known that the grandmother and uncle aren't biological relatives.] (00:29:15)
Continuity mistake: Simi enters the bedroom and the upper half of the bedspread is smooth. Aunt Claudia is holding a book with both hands, so she is not touching the bed. The front (somewhat aerial) view of the bed shows that the upper part of the bedspread has multiple ripples. (00:17:55 - 00:18:42)
Other mistake: At the end the camera bulbs would not work as they are electric. This is proven when the music starts after the creature leaves the area. (02:01:00)