Please?
The point isn’t to give her pleasure, not exactly. The point is to make her come. Her body is bound like a package for efficiency and to keep her exposed. “Helpless” doesn’t begin to describe it. “Helpless” implies the possibility of help.
Each time the timer clicks over he walks into the cell with the tool and gets to work. She writhed at first, squirmed, resisted, but these particular bindings provide plenty of handles and leave her nowhere to go. Each time he hauls her back to the center of the bed, switches on the vibrator, and gets to work.
She’s lost count, now, lost track of why they’re doing this or whether there was any point in resistance. The timer clicks and he walks in and uses the tool on her aching hot wet place and she comes. Not just once, either. She comes and comes until her pussy cramps, until she’s wrung out and sobbing for breath, until every nerve is throbbing and raw and her brain is too thick to think.
Eventually he turns the tool off and cranks the timer back up. She sags in her bonds, eyes unfocused, panting. He walks out, and she waits for fifteen minutes to tick by again.