It depicts the origins of the characters of Jacob (Mark Pellegrino) and his brother, The Man in Black (Titus Welliver), and how they came to be on the island.

She confronts Jacob's brother and claims she left the box for him, telling the young boy that he is "special".

The young Man in Black confronts Mother about Claudia's claims, and attempts to convince Jacob to join the other people with him.

Over the course of the next 30 years, Jacob (Mark Pellegrino) visits his brother (Titus Welliver) at the camp he shares with the other people.

The Man in Black reveals they have discovered a way to leave the island by digging wells in spots where "metal behaves strangely".

He tells her that his people have dug into the light from other locations on the island, and plan to create a system that will allow them to leave.

The corpses and stones are found centuries later by Jack Shephard (Matthew Fox) and Kate Austen (Evangeline Lilly), and dubbed Adam and Eve by John Locke (Terry O'Quinn).

Club stated "I have only one real criticism of "Across The Sea," and it's that when Lost deals directly with the transcendental—rather than just glancing at it—the show can get awfully gooey, and painfully blunt.

"[6] Jeff Jensen of Entertainment Weekly stated "Across The Sea" was "an unconventional outing that deserves props for benching its stars to give us a story that felt absolutely necessary for establishing the Big Picture context for the final act that is at last upon us.

"[7] Chris Carabott of IGN gave the episode a score of 6.8, saying that he felt frustrated that at this point of the show, it is not giving many answers.

James Poniewozik of Time stated "'Across the Sea' took a series that is deeply and richly psychological and character-based and moved it into the realm of the allegorical.

"[9] Maureen Ryan of the Chicago Tribune stated "For a lot of reasons, this was not an episode that goes in the Win column.