I assumed it was someone soliciting for charity or something similar when I got up to answer it. I opened the door to find my sister, Darlene, standin... there. Beside her were two suitcases. This was something I had not expected."Darlene? This is a surprise. Come in," I managed, helping her with her luggage."Thank you, Dal. I'm sorry to bother you, but I need your help," she said in a strained voice.I looked more carefully at her now that we were in the light and could see the dark shadows under. An elderly couple approached, a poodle trotting at their ankles.“Been a nice day,” said the lady.“Yes, really nice.” Diane smiled broadly. “One of the best.”In her bedroom, she delved into her pussy. Eyes closed, Diane vividly recalled the scene in the woods, pictured Jim between Mary’s spread thighs, his mighty length sliding in and out. What a thrill it had been, stumbling across her own private sex show. She’d seen a few porn movies but watching people fuck live — in the flesh, as it were —. I had to catch her masturbating again. That would not be to hard. Since the day I caught her feeling her pussy on the couch, she made sure she either did it in the shower or her bedroom. Of course, I wanted it to be in my room, so catching her in the shower feeling herself would have to be my best shot. I was hoping that she would be doing that tonight when she took a shower. It was almost time for her to do so anyway. My sister liked to wait every three days and I counted the days since her. “What happened?”“Cas, I’m so sorry. I swear we didn’t...”“Megan, it’s okay. What happened?”“Celia’s gone. We got back late this afternoon from Alex’s lab, and Celia headed straight for her room. I sat up in the front room talking to Mrs. Hollabrand for a few hours, and then she went to the kitchen to get dinner ready. I went to Celia’s room to tell her dinner would be ready soon, and she wasn’t there. I swear, we were in the front room the whole time. There is no way she got past us.”“But she.