West German writer Philip Winter has missed his publisher's deadline for writing an article about the United States. So far, he has traveled a lot, but has not written anything substantial, as he has been unable to find inspiration either in what he has seen, or in the many Polaroid pictures he has taken of his trip. He attempts to book a flight from New York City to Munich, hoping he will figure out how to write the article once he is back home, but is told at the airport that there are no flights to Germany because of a strike by German airport ground crews. He meets a German woman, Lisa van Dam, and her young daughter, Alice, who are also trying to book a flight, and manages to get them all tickets on a plane to Amsterdam the next day. In the morning, Lisa leaves Alice in Philip's care while she attempts to deal with her emotionally fragile ex-boyfriend, leaving Philip a note in which she tells him to take Alice to Amsterdam, and that she will meet them there soon.
As Alice and Lisa lived in Amsterdam at one point, Alice speaks some Dutch, and she suggests showing Philip the city while they wait for Lisa's flight. Saddled with someone else's child and short on money, Philip begins to get irritated, cutting short the sightseeing trip and no longer finding Alice's constant demands for care very endearing. When they go to the airport to meet Lisa's flight and find out she is not on the plane, Philip intends to leave Alice to wait for her mother with the authorities while he continues his journey home, but she is upset and locks herself in a bathroom stall. Feeling sorry for the girl, Philip remembers she mentioned visiting a grandmother in Germany, and offers to take her there, but Alice does not remember where her grandmother lives. He reads Alice a list of city names, and "Wuppertal" seems to ring a bell, so they get on a bus.
Although Alice cannot remember her grandmother's name or address, she says she is sure she will recognize the right house when she sees it. After searching Wuppertal for two days using the Schwebebahn and a rented car, Alice realizes her grandmother does not actually live in the city. Fed up, Philip drops Alice off at the police station, and then tries to unwind at a Chuck Berry concert. When he returns to his hotel, Alice, having escaped from the police station, gets into his car and says she now knows where her grandmother lives. Philip is glad to see her again and drives away, while she tells him that, during her interview with the police, she remembered that she and her mother had been the ones who lived in Wuppertal, but her grandmother, whose name is Krüger, lived just a short train ride away. Alice also finally shows Philip a picture of her grandmother's house that she has in her purse.
Philip and Alice begin to search throughout the Ruhr area, and, miraculously, they eventually find the house in Alice's picture, but the current resident does not know Alice's grandmother. With no solution in sight, they go swimming, releasing their frustration by playfully shouting insults at one another. Now virtually broke, Philip decides to go to his parents, who live across the Rhine. On the ferry, a policeman from Wuppertal spots Philip and Alice and informs Philip that both Alice's grandmother and Lisa have been located. The policeman puts Alice on a train to meet Lisa in Munich, and, though Philip has no money for a ticket, Alice produces a 100-dollar bill from her purse so he can come along. En route, Alice and Philip ask each other what they will do in Munich; Philip says he will finish writing his article, while Alice just raises her eyebrows. They open the window of their train compartment and look forward together.
