Mike Foster, a securities trader, has grown accustomed to his quaint and secluded life with his family in the high residential hills of California. It was a life of convenience, until his reality became disrupted after a failed kidnap attempt on his wife and children. Feeling helpless and unguarded, Mike meets with his home's high tech developer who decides to install an android patrol guard, named Dell, to keep watch on the property. This new robotic addition to the family proves suitable for their protection, until Mike discovers a glitch in Dell’s behavior. Growing attached to the property itself, Dell begins to question Mike's ownership and authority while showing signs of hostility. After a power surge disables the home's security, Dell believes that Mike and his family are a threat to the house itself and attempts to eradicate them by any means necessary.