As Tom had gathered all the cloths he thought he needed he grabbed Jen around the waist as he lead her out the back door where they could get dressed out of sight of the party.
Unfortunately the blow job Jen had started to give him meant he still had a hard on when they got to that quiet place and Jen did notice it as she licked her lips.
So when Jen pretended to lose her balance falling to the ground she was just able to fall on him and before he was able to recover she had slid his rod into her pussy which she began to milk.
Tom at first thought it was going to be a bad idea with Jen's mother on the way but as she rode him he went along with it even grabbing her waist to continue, not thinking to well until after he shot his load into her.