On the Water (2020)

When Cecilia's brother disappears while swimming near the family cottage, she must hunt for his whereabouts in the slender time between an instinct and a crime. Out in the Canadian back country, on a big lake that lies along the course of the Madawaska River, there is a summer home whose heyday was in the 1970s. Cecilia and Ethan, the youngest generation to visit, are siblings who have come for one last weekend at the end of the season. Though they are polar opposites, there is a feeling of connection when they spend time together at the lake. After a small argument on their first day, Ethan goes for a long swim. A strange boat appears and Cecilia watches from the dock while her brother boards and they take off. As the sun starts to set with no sign of Ethan, Cecilia begins tracking him down. She follows every clue that she can think of to no avail. After midnight, as thunderstorms roll in, Cecilia gives up for the night and heads back to the cabin alone. She is shocked when she arrives.