Summer 1910. Several tourists have vanished while relaxing on the beautiful beaches of the Channel Coast. Infamous inspectors Machin and Malfoy soon gather that the epicenter of these mysterious disappearances must be Slack Bay, a unique site where the Slack river and the sea join only at high tide. There lives a small community of fishermen and other oyster farmers. Among them evolves a curious family, the Bréfort, renowned ferrymen of the Slack Bay, lead by the father nick-named "The Eternal", who rules as best as he can on his prankster bunch of sons, especially the impetuous Ma Loute, aged 18. Towering high above the bay stands the Van Peteghems' mansion.