Dominic will show up again. I think the cycle or rebirth spiritually in Jacob by all who die is part of why Kate hears from jack they have to go back. I think that's why Hurley is visited by Charlie. If this island is some dimension of hell and the Jacob spirit can reach out to Kate via Jack and Jack via Hurley, and Hurley via Charlie to go back, it wants them back. It knows them. I think the appearance of Charlie will affect Claire because she would likely do what he "says".

It's like the palantir in LOTR. Jacob "shows" you what you want to know. I think the island and Jacob worked really hard to get control of Charlie. But he resisted the dreams and he kicked the heroin. Jack is a likely target for guilt as well.

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