The game's prologue opens with Ethan Mars, spending time with his family for his son Jason's 10th birthday. While at a busy mall, Jason wanders off and Ethan frantically searches for him, soon finding him outside on the street. Jason runs back to Ethan, unexpectedly into the path of an oncoming car. Ethan jumps out, trying to save Jason. However, the car crashes into Jason, killing him, while Ethan himself is injured and falls into a coma for six months. Two years after the accident, Ethan is suffering from severe depression, agoraphobia, and blackouts that last for several hours. He is estranged from his wife, and his remaining son, Shaun, is distant with him While at a park with Shaun, Ethan has another blackout, and wakes to find Shaun missing.
Source: https://en.wikipedia.org/wiki/Heavy_Rain