Driving back to the cabin

We settle our bill and leave the restaurant, driving back to the cabin in a silence filled with sexual tension.

I wonder if I should say something to my step-mom, but she is focused on driving, but has a contented smile on her face. I feel tempted to reach a hand across and touch one of her big tits, but I decide against it.

About a minute passes, then, without taking her eyes off the road, Millie says:

"Well, are you interested?"

I wonder what she means, but I think I can guess, so I just reply:

"Yes, definitely."

"Good." Millie says and nods, smiling a small smile and reaching her hand over and gently rubs my thigh, then puts it back on the steering wheel and focuses on driving again.

I sit there feeling my cock getting hard and pushing against my pants, wondering if this is actually taking place. Am I about to fuck my big titted step-mom in the ass?