"[returning to Dream from the old Memory Chamber] You are a most unusual traveller, my friend. The vision you witnessed here last time served you well, yet you still see Dream as dark and slightly dangerous. Why? I see the answer in your need. You're not just looking for visions this time. You seek the very memories themselves. The one you know as Yeesha is still here. She's been unable to return to her waking mind, because her connection with it was severed prematurely. Come. I will take you to her. Yet the strands of Dream are shifting, even as we approach. I sense the connection reopening, so when we reach her... [finding Yeesha's Dream-form, with a monstrous creature connected to it - Sirrus' Dream-form] Interloper! That traveller has no Guide. He's using Yeesha's memories to remain anchored in Dream. Otherwise, he would be lost and quickly crushed amid Dream's constantly shifting waves of possibility. Why is she not aware of him? There! Do you see the anchors he's using? They are very powerful memories, which both Yeesha and the traveller have in common. Somehow, he's jumbled them up and is using the confusion to hide himself from her. She cannot return to her waking mind while he is attached. You can release her. By entering both memories and replaying them correctly, you may startle the traveller enough so that he reveals himself. I will send you into the first one now, and await your return."
January 1, 1970
https://en.wikiquote.org/wiki/Myst_IV%3A_Revelation