Mona and Robby are a young couple in love. Robby has just landed his dream job, and they've scored an amazing deal on a spacious, if run-down, flat. Never mind that it requires quite a bit of renovation. Never mind the neighbour's constant fighting, and screaming baby... Never mind that Mona is suddenly plagued by night terrors which grow more intense every time she falls asleep... Robby is eager to start a family, despite Mona's hesitation. Eventually, Mona's issues spiral dangerously out of control as she becomes convinced that she is being attacked by a mythical demon - the Mare - intent on possessing her unborn child.