Lillith pretended to ignore his protests as she made her way to the cavern. She kept an ear out for any passersby who might notice the little tied up imp being carried about in his boxers; it wasn't by any means likely that they would run into anyone, but it wasn't impossible, either. When they reached the cavern, she propped him up against the wall and patted his head. 

"I'll be back shortly. Wait here like a good boy, and I'll bring you back a treat."

She ran a feather-light fingernail along his inner thigh, kissed him deeply, then gave him a little wave as she walked away with a smirk. Her "errands" wouldn't take long, and with her vampiric speed, she'd be done and back in less than ten minutes.

Not that [i]he[/i] needed to know that.