"Sandy McCartney", a thirteen year-old London schoolboy is picked as exchange student by the German couple Erik and Charlotte Neufund, who took the teacher's cue to enter the program, desperately seeking a friend fro troublesome, anti-social daughter Fiona (aged 16), without consulting her. They expected a girl, so want to send back Sacchidananda, a straights AAs schoolboy who is proud of his Indian roots, but after tasting his quaint self-confidence and oriental chivalresque championing her, Fiona joins her decent sister Annika's objection to expelling a foreign guest who did everything right, so the program stands. Sandy proves a brilliant miniature-Gandhi who brings lost cohesion back to the family, which gets into crisis when Erik's tax problems compromise their livelihood and Charlotte is found out having an affair by the kids. Meeting Sandy's parents in a grand London mansion is another major surprise fro the Germans.