In 1914 Lars Tobiasson-Svartman is covertly measuring the depths of Swedish coastal waters. A man of discipline and obsessed with exactitude, he is more comfortable on naval vessels than he is in his loveless marriage back in Stockholm. On one of his missions, Lars discovers a feral but beautiful woman living alone on a remote island. Passion, suspicion, and violence are awakened in him and soon he is living a double life-lying to his wife and his superiors and submerging himself in a pool of deception that has devastating consequences.