how to get back to heart of island

how do i get back to the heart of the island at the end of part 6?

I'm sorry that no one got back to you about this. I'm not real sure what you are asking. Can you tell me more if you still need help? I promise to be more vigilant about checking back.

Use the whole in the sanctuary where Nick felt through. When you hover your mouse over it, there'll be door-sign. When you use this, you arrive in a cave. Walk across the cave to the right and you end up in the heart of the island.

in part 4, where is John?