This episode was all about Jacob, the Man in Black (MIB) and, it turns out, the woman that killed their real mother. This is what we learned on "Across the Sea."

- Jacob and MIB are twins born to a woman that arrived on the island via ship wreck and was then killed by the island's unnamed guardian (we'll call her Woman).

- MIB and Jacob are eventually told by Woman that she made it so they can never hurt each other, and - when they are 13 years old - she shows them a glowing body of water that she says contains all the good life force of man. It must be protected at all times because men always want more of it and this is a dangerous thing. One of the boys will end up as its protector.

- After receiving a visit from his dead, real mom - who shows him that her fellow shipwrecked passengers are still alive and "his" people and that his home is elsewhere - MIB is determined to get off the island. He leaves and goes to stay with these people, while Jacob stays behind with Woman, even after she admits she killed his real mom.

- The "rules" between Jacob and MIB date back to Woman tapping into the island's powers. Also, MIB makes up rules for a backgammon-type game Woman made for him and which is always plays with his brother.

- The frozen donkey wheel was constructed by MIB as one of his numerous attempts to get off the island. He and his people found pockets of electromagnetic energy and dug whenever this took place. They found the light emanating from underneath the island. When Woman learned of this, she knocked out Jacob and burned down his village, killing all his people.

- MIB was turned into Smokey when Jacob, distraught over his brother committing matricide following the incident above, threw him into the golden water, which Woman had warned him was "much worse" than dying.

- The Adam and Eve corpses Jack and Kate found early in season one are the original remains of MIB and Woman, left lying in their old cave home by Jacob, who also included a black and white piece from the game the siblings played together.