Stuck in Angoulême between her uncle, who composes classical music, and her aunt, who is a fan of contemporary music, young Irène finds life boring. Fortunately, there is swing music which illuminates her days. So when, one day, Raymond Serre and his swing orchestra come to Angoulême, she seizes the opportunity to slip the copy of a song she has written into the pocket of one of the musicians. The trouble is that while she is doing so, the train she has boarded pulls out.