**SPOILERS** Coming over to the Frame home in rural USA to be taken in as a member of the family young Emil Buckner, Skip Homeier, is anything but your typical American boy in fact he was brought up in Nazi Germany and brainwashed to grow up and become a future Aryan Superman in the Hitler Youth. That fact that Emil's dad who was thrown into a Nazi concentration camp where he eventually died for speaking out against the Fuhrer, Adolph Hitler, made Emil look suspicious to his Nazi overseers who felt that he may well become like his dad, normal, when he grows up. The Nazis decided that he didn't have what it takes to become a good and loyal member of the Nazi Party and sent packing to the US to stay with his old man's brother-in-law Mike Frame, Fredic March, and his future wife Leona Richards, Betty Fields.
Not getting the hint that he was a total wash out, in him not having what it takes to be a good Nazi, from his beloved Nazi Germany Emil ,because of him being brainwashed since he could barley walk, still thinks that he's a full fledged Nazi Superman and goes so far as to parade around the house, this in 1944 when the US was at war with Nazi Germany, with his Nazi or Hitler Youth uniform. Emil makes a complete jerk of himself in him trying to be a spy for the Fatherland and at the same time blowing his cover, by bragging about it, and not realizing that the Fatherland, wanting nothing at all to do with this nut, had him unceremoniously kicked out!
Acting like a Nazified version of "Dennis the Menace" Emil is all over the house and even at school trying to prove to everyone, including himself, what a great Nazi Superman he really is. For a while Emil does get his classmates to go along with his crazy antics that he picked up back in Germany while in the Hitler Youth. Emil has his classmates take night marches into enemy territory and staging roadside ambushes, all in fun of course, while being disguised in camouflage so that the enemy, whoever he is, can't see them as well as familiarizing themselves with all kinds of arms and ammunitions, German of course.
Emil goes a bit too far when he first comes to deal with Leona, his Uncle Mike's fiancée, being Jewish as well as his determination to steal Mike's mail that he gets from the War Department. Mike is one of the country's top chemist and is working on a top secret project for the US military, the Atomic Bomb?, and Emil wants to get his hands on what he's doing by stealing his private notes and mail and send it back to the Fatherland. In the case of his future aunt Leona the fact that she's Jewish is enough to drive Emil batty in thinking that he'll be forced to live under the same roof as she is when she marries his Uncle Mike: a fate worse then death itself for the cute but somewhat not all there in the head little Nazi.
Two things happen that turn Emil around in his mission, or what he thinks it is, in serving his Fatherland. Confronting Leona about her being Jewish, in the most vulgar of ways, she slaps Emil across the face that shocks the very self-assured and arrogant young man in him, ,an Aryan Superman, not only being whacked by a lowly woman but a Jewish one at that! The second incident that brings Emil back to reality has to do with his getting into a fight with fellow student Stanley Dumbowski, Rudy Wissle. Stanley being a Polish/American whom Emil felt to be inferior to him was able to take him on and give him a bloody nose and even later force Emil, with their teacher Miss. Richards looking on, to apologies to him in front of all his classmates; What An Insult!
With all his arrogance about being a good Nazi now in question the only thing that can bring back Emil to his fantasy world of serving Fuhrer and Fatherland is to get his hands on Uncle Mike's secret papers and send them back to Germany, by US airmail?, to show everyone back home what a good German, or Aryan, he really is. Emil is stymied in his plan to serve the Fatherland when he's caught red-handed, with his hands in Uncle Mike's drawer, by his young cousin Pattie, Joan Carroll, who just bought him a birthday present, a illuminated watch which he always wanted for his crazy nighttime war maneuvers. All at once Emil graduated from just being just a pesky and uncontrollable but somewhat harmless young boy to a possibly up and coming psycho killer the very type of person that would make those back in the Fatherland, the Nazis, very proud of him.
Intriguing movie about how a young man can be so seriously brainwashed that he goes against his best interests to serve a country and ideology, Nazi Germany, that did nothing but harm him and his family. Where at the same time having him try to destroy, in his own childless way, the country and its people that did nothing but help him in every way it and they could despite his dislike of both of them.
Emil does see the light at the end the movie, or tunnel, in how he was treated by his Uncle Mike and especially Leona, a Jew who in his mind is the eternal enemy of his beloved Third Reich, as well as his victim of violence Pattie in the kindness and understanding as well as love that they all showed to him.This kindness and understanding is something that he never would have gotten, if he did what he did here back there, in Nazi Germany.