Helen Turner is a young and beautiful woman, married to a much older man. One spring morning she walks out to her mailbox. The letter in her hand is addressed to a stranger, a bush pilot. She slips the letter into the box, and raises the red flag. What Helen doesn't know is that the letter she has just mailed will change her life. Looming ahead is a series of mysterious explosions, an airplane crash, and the fires of passion. Helen will be forced to choose between the man she married and the man she loves.