I'll keep [your] dirty little secret.
Witness to the scene and listener of the confession, I have your half-truth and her half-truth and his crooked smile. I know the story you wonder about. It's all pieced together, all been carried out and convened in my mind.
"Really?" My eyes widen. Innocent smile for this innocent girl. No one else will ever know what I know.
And of me -- you know naught.
In the darkened corners no one peers into, let's make our own quiet chaos.