...is Karen.

Karen is curled up on the loveseat, passed out. She's still in her cocktail dress, her hair is mussed and there's a wastebasket under her face. She's muttering and mumbling snippets of dance music in her sleep.
Where is Jenna?
You and Tara look around for a few minutes. The soft sounds of snoring come drifting up from the basement. Zoe.
You make your way upstairs. The only light is coming from under your bedroom door. There are soft sounds of quiet voices from the other side. As you get closer you can make out words.
"...shouldn't be..."
"...just relax, Jenna.." that's Jack's voice. What the fuck?
The door is closed and locked, but it wasn't pulled tight enough, and you are able to push it open.
"Oh...that feels so good...but you shouldn't..."
"I can stop. Just say the word...."
"Mmmm....."
You push in to the scene that your ears prepared you for.
Jenna is sprawled on the bed. Her dark gray cocktail dress is bunched around her waist. She's got her eyes closed and she's touching her breasts.
The source of her condition is obvious: Jack, clad only in his briefs, has his face buried in Jenna's cunt.
"What the fuck, you guys!!" Your angry shout cracks through the room.
"Oh, my god, Ms. Jenna!!" You didn't realize Tara followed you up.
Jenna squeaks in surprise, sitting up rapidly and trying to push her dress down, as Jack rolls off the bed on the side away from you.
"J...James! We... we didn't know where you'd gone!" Yeah, because that's an explanation for what you just saw.
"Jenna...I can't even..." So many different emotions are running through you, but the strongest isn't anger, or even betrayal. It's arousal. It had been a hot scene to walk in on.
Why were you working so hard to restrain yourself with Tara while Jenna was getting her pussy eaten out by Jack? You glance sideways, and Tara looks.... intrigued?
"I'm... I'm sorry...I don't know what came over us..." Jenna's face is red.
You burst out laughing, looking at Tara. Then you push the door all the way closed.
"Well, don't stop on our account! Looks like you were having a good time." You push Tara towards the bed, unbuttoning your shorts.
"R....really?" Jenna is confused. "You....you aren't mad?"
"Oh I'm fucking pissed as hell, Jenna. But..." you drop your shorts, "I think there's something we could do to fix that..." Jenna looks from you, to Jack, then Tara, then back to you. Then... amazingly... she nods.
"Fuck it!" Jenna giggles. "Why not?"