To obey out of fear

"Mmi'll mme mmood," Heather reluctantly says, fearing what might happen to Jenni or herself.
"A wise choice," the voice says, "And what does your so-called friend say?"
"Mmi...mmill...mme mmood mmoo. Mmust mmon't mmurt mme."
"If you do not act up, I won't hurt either of you. If your good behavior changes, however, I will not hold back against you. You are not the first people I have done this to, after all. Now don't forget to breath deeply."

Both young women are confused by the cryptic nature of his comment until the notice an unusual smell.  After less than a minute of exposure, Jenni's eyes slowly roll into the back of her head and it drops down.  This inspires Heather to struggle with all her might, but it is far too late.  In about thirty seconds, all of the strength leaves her body as well, causing her head to settle down next to her friend's.

After an indeterminate amount of time, Jenni begins to stir from her second induced slumber of the day.  It takes her a couple of moments to awaken fully.  This happens when she tries to stretch, but finds that she cannot move her arms.  No matter how much she tugs, they are stuck.  All of that struggling causes her to notice a weird feeling against her hand.  It feels like...the warm flesh of someone's back.  Panicing more now, she lifts up her head and sees something unexpected....

The face of her **** friend Heather.

Being mere inches away from her friend's face makes Jenni feel a little uncomfortable, so she tries to back away.  She quickly discovers that her legs feel heavier.  By turning her leg to one side and looking off in that direction, she learns why.  Her leg is tied to that of Heather's as well, around her lower thigh and calf.

Looking back up to the ceiling, she spots a long rope tied to an unseen location.  She follows its path down and sees that it is tied to a rope that is subsequently tied around the waist of herself and her friend.

She wriggles around more in fright, trying desperately to find a loose rope or two.  All of that movement has a different effect than she intended, however.  It causes a strange sensation in her chest.  Upon close inspection, it is apparent why.  Heather's **** form is tied so tightly to Jenni that their nipples are rubbing against each other.

The only solace she can take in her status is that her mouth is free of a gag...at least for the moment.  Her mind can only wonder why.  Her thought process is interrupted by Heather's voice.

"....ohh....please...tell me that was a dream...," she says.
"Sorry," Jenni says, "It's not."
"What....has he...she...done now?"
"I don't know what that person has in mind, but they have tied us together."
"No way," Heather says, the shock seemingly helping her awaken.

****, the voluptous co-ed beings to struggle against her bonds, eliciting the same response as before.

"Ohhhh...please don't do that," Jenni says, "You don't...know what that is doing to me."
"What do you...," Heather starts to say, before feeling the same sensation, "So-sorry. I didn't know."
"Don't worry about it. It....wasn't a bad feeling..."

Jenni does not realize the magnitude of her words until after she had uttered them. A small silence comes across the duo, but that does not last.

"It's about time you two woke up," the mysterious voice says, "Are you ready for the next test?"