Die Flut ist pünktlich

A corpse is washed up on the beach of the North Sea. The deceased is Alexander, husband of the beautiful Bettina. They have been coming to the island for a long time and possess a cottage there. At first no one doubts that Alexander died of an accident, but the young policewoman Maike, who has known the family since her childhood, thinks that Alexander should have been familiar with the mudflat. Did he kill himself?