It's a peak that she's teetering on, ready to fall off of at any moment, and the second that Kate rubs a little faster, it only takes a series of short thrusts to finally bring her over the edge.

She leans back against Kate, relying on her to hold steady as her body quakes with the force of her orgasm, and then falls forward, riding it out with her forehead pressed against Bill's shoulder.

"Holy crap," she breathes.