Happily married Michael and Karen Carr call the police after Karen is held at knife point during a failed robbery attempt in their home. Before long, one of the responding officers, Officer Pete Davis, helps arrange the installation of a new security system, taking extra interest in the couple's case. As a result, the grateful Carrs invite him to stay for dinner and they strike up an unexpected friendship. However, as the lonely policeman develops an intense fixation on Karen, his take on friendship develops into a dangerous obsession soon becoming the Carrs' worst nightmare.