For centuries, people have celebrated every Midsummer's Eve at an ancient spring near a small Swedish village. On that special night, when unmarried men and women dance and some unusual activities are permitted, the Bridal Spring has special powers. Vilhelm Moberg introduces four musicians on the last day that each one will ever know: a curmudgeonly fiddler from the 1930s, a sad and conscientious key-harp player from the plague era of 1711,...