Sick Simon, aka the true Simon, is who is writing the story you play.  He is a victim of a hit-and-run accident when he attempted to help an old man crawling in pain. After the accident, he lost use of his waist down, which confined him to a wheelchair. In endings 1-3, he shoots himself and upon the player finding a book in his room, they are sent to a bloodied and twisting nightmare world. Said nightmare world is a depiction of S. Simons mind, and in the world, the player must platform on books that have "SUICIDE" written on them, filling two pages. When you reach the top of the platforming, you must jump into water which will lead you into the final battle with him, explained below and in the BOSSES tab.

The final battle is a unique one, with special Faceless enemies you have to fight in order to gain four valves. In this battle, you play as Book Simon, instead of Simon, the version you used to play as.  S Simon will use psychokinetic powers to move boards and boxes scattered in the room as he is in a barred off room. If he hits you with these objects, you will take damage. Morphine syringes are still usable, but they are not found in this room. Once you finally get all four valves and spin them into place, the bars enclosing S Simon rise, and you lose control of your character. Book Simon will then, a bit clumsily, will walk over to S Simon and begins beating him up. He eventually knocks S Simon out, and out of his wheelchair, before climbing over him and chokes him to death. With S Simon dead, B Simon collapses too, symbolizing S Simons suicide in the real world. With their deaths, the game ends, and you are brought to the cutscene. The image on the right is B Simon finally ending S Simons life, indicated by the health bar above.