The Sleepwalker (2014)

An unmarried young couple, Kaia and Andrew, are renovating Kaia's secluded family estate. Their lives are violently disrupted upon the unexpected arrival of Kaia's half sister, Christine, and her fiancé, Ira. Prior tensions and jealousies burgeon as new alliances form and childhood patterns resurface. As the days grow darker and the nights more disturbing, Kaia is forced to confront Christine's increasingly tangled perception of reality, which in turn may have begun to alter her own. When one of the four characters goes missing, the three left behind are flung into upheaval trying to fill in the blanks.