Theo thought for a moment. He didn't want Stephen to be burdened with the knowledge of his contacts with the Order, which meant that he needed a pensive. No matter how good an Occlumens he was, you had to open your mind to be able to look into someone else's. Occluding while performing legilimency was simply not possible, and there could always be backslashes.
Standing up, he called Mimsy and asked her to bring his pensive where he put some of the more sensitive memories. There was no way to put all of them there, it wasn't viable, so he chose the most important once then thought of inane memories before turning back to Stephen.
"Now I'm ready," he said, raising his wand as he faced Stephen. "Just try to feel me first, so you know the signs, then try to throw me out," he said. With a flick of his wand and the spoken incantation, he entered Stephen's mind, not hiding himself but letting him sense him there.