Flashback: How did it come to this?

The same Saturday morning, some hours after Sarah had taken the pills:

Adam hears moaning from Sarah's room. Concerned that his sister did somehow hurt herself, he opens her door to check out what happened, and he sees Sarah lying face down in front of her desk. Assuming that something has happened, he moves closer, only to realize that his sister is not wearing any clothes at all. She is completely naked!

She is lying stretched on the floor, with her nude back side revealed too him. Her arms are stretched past her head, long blonde hair scattered in her back. He can see side of her tits pressed between her upper body and the floor. A thin waist leading to wide hips. Sexy tight ass, her cheeks and thighs pressed together, hiding anything extra. Fit thighs and long slender legs. A spectacular view.

Seeing his sexy sister naked, even from behind, he cannot help it, and Adam gets horny, his 4 inch cock making a small tent in his jeans.

“Down boy, that's my sister! What if she is hurt? Focus!” he mumbles too himself.

"Sarah?". No reaction.

Nobody else is at home. Their parents divorced, the two siblings live in a house with their mother, who is working even on Saturdays. Adam had **** but to move in closer and find out what the situation is exactly, to make sure that his sister is alright.