1940's, WWII 

Jill Winters, 14, has been sent to stay with her grandmother in Maine while her father, a famous singer, is on a U.S. tour and her mother is visiting her dying brother in Newfoundland. It is the summer of 1942, and German U-boats patrol the shores of the North Atlantic. Jill is terrified that her mother's ship will be torpedoed and nervous about the possibility of U-boats in the area. Adding to her worries are the mysterious goings-on in Winter Haven. Even her grandmother is secretive about the Sunday night meetings she has with her friends. When Jill intercepts a carrier pigeon with a message in German, she begins to suspect that someone in the community is guilty of treason, and she has no idea whom to trust. After the town's July 4th clambake, her life is threatened when it becomes clear to the spies that she has figured out their identity. The ending is not neatly tied up and leaves some unanswered questions.