I was certain that he could not see me.

He passed between the scene behind which I stood and a set piece, went to the wall and pressed on a spring that moved a stone and afforded him an ingress.

He passed through this, and the stone closed behind him.
I waited for at least thirty minutes and then pressed the spring in my turn.

Everything happened as with Erik.

But I was careful not to go through the hole myself, for I knew that Erik was inside.