From the angle he was at, Jim could see between Mark's hairy thighs, where his balls were hanging and swinging. He could also see the thick stalk of Mark's cock, where it was plugged into Cathy's naked, bald pussy. About then Cathy sighed, "Oh Mark, here it comes baby, I'm gonna cum.... oh yes ... that's it ... right there ... Awwwwweeeeee!!!"
And, while Cathy had what was obviously a massive orgasm with her pussy wrapped around her brother's thrusting boner, he began to react too. "Oh yeah, Cat, me too ... Oh Yeeaaaaahhh" Jim gaped as those hanging balls drew up an inch and Mark jammed his cock deep into his sister's pussy. Then his ass cheeks clenched and he grunted, three times in a row. Jim knew that each grunt signaled that a long rope of thick white sperm was lancing into Cathy's pussy ... her self-confessed unprotected pussy ... where it was no doubt being packed into her womb where it would do the most damage possible.
Meanwhile, Cindy, who had been frantically rubbing her own pussy while watching her friends fuck, squealed, "Save a shot for me Mark!" Like he was following the direction of some author, Mark jerked his spitting cock out of Cathy and turned toward Cindy, who dove on his cock like a starving child. Her mouth swooped down onto his cock, capturing the head and a couple of inches, while her hand jacked on it, milking the rest of his cum into her mouth. Jim glanced at Cathy, who lay there, her legs still wide, thick white fluid oozing from her swollen pussy lips. Cathy lazily turned her head to watch the other two as she rubbed that fluid right back into her pussy!
Jim realized two things at that moment.
The first was that he had stumbled into the open doorway, and was completely exposed to those in the room. The second was that he had a killer hardon. In fact he was harder than he'd ever been in his life. He didn't understand what was going on, but it was the sexiest thing he had ever seen. He was breathing hard. His hands were at his side, but it was all he could do to keep them there. What he really wanted to do was drop his pants and ease the pressure in that stiff prick in his pants.
Cindy heard a noise at the doorway and looked. She squeaked "Uh Oh!" about the time Jim saw his daughter lift one of her cum-soaked hands to her lips and begin licking her fingers clean.
He suddenly felt light headed, and the room began to spin. Then, there was blackness.