In one of the final scenes, Vivan hits Madeline in the forehead with a hammer. Madeline is seen on the floor with a cut over her right eye, with a fair amount of blood. Vivan then leans towards her to see if she is alright, but there is no more blood on her forehead. When Madeline bites Vivian, the blood returns.
When Madeline is brewing her tea in the strainer and suddenly drops it, you hear the sound then in the next shot (a second later) she drops the chain.
The film is set in Regina, Sask., as indicated by the fact that Vivian is seen driving past the Saskatchewan Legislative Building. However, Patricia's landline, cellphone, and fax numbers have a 206 area code, which serves the Seattle area, instead of 306, which serves Saskatchewan. Maybe Patricia's from Seattle and didn't want to change her numbers.
In the scene in which the main character takes the trash out, when she turns to walk back into the house, a crew member can be scene, quite easily, viewing a monitor in a dark door way in the house.