The Lewise family believes that their new neighbors the Hellenbecks are from outer space. The couple and their only child are strange, and seem to have little or no knowledge of 20th century customs and behaviors. Soon strange things begin happening and a strange heat-seeking device tries to kill the Lewises. The Hellenbecks reveal they are from the future, and came back in time to have a naturally-born child (which is forbidden in their future). Together the two families manage to defeat a killer-android and the Hellenbecks depart rather then endanger their new found friends.