In 2010, health problems persuaded the moviemaker to finish what he began via post-production.
"He had shot about 81 percent and there was enough material to make a suspenseful movie," Sluizer's daughter Anouk told the AFP. "My father had to find a creative solution, about which I cannot say much, as there is an element of surprise."
River's family seems estranged from the finished product, as they released a statement to Deadline.com saying that "Joaquin Phoenix and his family have not been in communication with the director, nor will they participate in any way."
The film will debut at the Utrecht festival September 27.