Lydia takes some safety measures first

"For this to work, we´ll need something toestablish trust." Lydia explains. "I mean sure, John trusts you, but this is about you fucking me, using my body. How do i know you won´t just go off and sleep with 5 other women besides me? I´m worth more than that."

Not sure what shes getting at, you respond: "So you dont want me to sleep with anyone else while we try this...got it."

"Well", Lydia smiles, "I´m afraid its not that easy. We had a different idea, or I did."
She nods at John who leaves the room, supposedly to go to his. While hes away, Lydia strokes her hand along your thigh and whispers: "I cant wait to feel you stretching me out. Trust me, our proposal is worth it. Take it, and I´m all yours."

Then John returns, holding a small box in his hands, which Lydia takes. She opens it, and takes a silver chastity belt out.

"With this" she explains, "I´ll know you dont sleep with other women. I´ll take it off to let you fuck me, and its gonne be worth it, but the rest of the time, you´re gonna ba locked like John. What do you say?"