Dad was molested by his teacher
Family was prescribed anti-psychotics. Possibly for the Dad's PTSD from the war
Son was traumatized after witnessing the death of his dog, so he was being given the anti-psychotics in his food to help him sleep and get through it
Dad started drugging the daughter's food with the anti-psychotics and molesting her
Daughter knows it's being done to her, tries to tell brother, brother doesn't believe her. Mother denies it's happening despite the signs
Dad drugs her too much one day, and she dies
Dad tries to dispose of the body in the river, but the body washes up ashore
Autopsy reveals history of abuse
Son has total psychotic break from the death of his sister (and possibly seeing the body). Has delusions his sister is still alive, still sees and talks to her
Events of story happen
Dad tries to find daughter's diary to dispose of evidence, but son has it
In most routes, dad grabs a gun and attempts to flee on a boat. Is either arrested or killed
Grandma comes back to help take care of the family
Depending on the route you choose, the boy can either come to terms with what happened and move on, have a total psychotic break, die and reunite with his sister in heaven, or lose his entire family. If the son confronts the father in the father's route, the dad realizes he's become just like the teacher that molested him, and either turns himself in or kills himself.