Continuity mistake: A few times when Emily fights with the intruder, her hair changes from being in a ponytail, to down. (00:46:30)
Visible crew/equipment: When Emily is driven home to her mother and the mother opens the car door, a camera and microphone boom are visible in the reflection of the car window. (00:59:05)
Revealing mistake: At the end a character is killed and you see him lying on the floor, dead, but still breathing.... (01:43:00)
Continuity mistake: Emily's hair scrunchie appears in her hair as she is answering the phone and seems to have fallen out during the struggle but reappears and disappears several times throughout the attack.
Continuity mistake: The shoebox with the money in it goes from no rubber band around it to having one around it, when David takes it out of the bag.
Visible crew/equipment: In the loft scene when Stephen asks David to kill his wife, a crew member steps out from behind the cabinet behind Stephen.
Answer: Steven needed money and his wife was worth a lot of money. She was already having an affair and was planning on leaving him. If she left, Steven could be left with nothing and still in financial troubles. By killing her before she divorces him, he'd be entitled to her wealth, plus the money from her life insurance policy.
Bishop73