Silent Fall by Bruce Beresford

5.20

Having seen the double murder of his parents, autistic youth Tim Warden is sent to therapy with controversial therapist Dr. Jake Rainer. Jake tries to probe the silent child about what he saw, but he gets more details about the Wardens' household dynamics from Tim's teenage sister, Sylvie. As he spends more time with the siblings, Jake learns that the Wardens' marriage was not as perfect as it seemed, and he uncovers other new details that might help solve the crime.