An alien from another planet lands in Dennis room in a quest for peace and quiet... but Dennis wants to show him around! A mad romp ensues with Dennis taking the alien to Mr. Wilson's house. When Wilson calls the police he is thought to be a quack and carted away. Dennis and his family go on a trip on a train, however Dennis forgets his suitcase. Mr. Wilson, trying his best to make sure Dennis leaves, runs onto the train to give him the suitcase... but, he cannot get back off and is now stuck with Dennis on the train! While there, Dennis sees a man with a trenchcoat and a briefcase and figures him to be a spy. With Mr. Wilson unwillingly helping out, Dennis proves the man to be a spy. Dennis and Margaret both find a bottle from which a Genie emerges. They argue over who gets the wishes, but agree on one wish each. Margaret uses her wish to make her doll come to life, which gets her into jeopardy, and Dennis uses up his own wish to save her. (thetvdb.com)