Jack is asleep in his tent on the beach when Juliet wakes him up. She tells Jack that since he brought her to the camp, Sayid and the others have not trusted her and think she is there to hurt them. Jack says that he will protect her, but Juliet then tells him that they are right; she is still working for Ben and she has been sent to the camp to do tests to find out which of the women are pregnant. Jack asks her why she is telling him this, and she tells him that she saw Sun's baby the night before, and that she doesn't want to live Ben's dream anymore.
Juliet says that Sun and the baby will die in about a month if they do not leave the Island.
The 'Operation' part of the title refers to Juliet's mission to infiltrate the survivors' camp. In warfare, a 'sleeper' is a spy, saboteur or terrorist planted in an enemy country who lives there as a law-abiding citizen until activated by a prearranged signal.
Scan of the 'making of' article from the Lost Magazine
The production code/mobisode number for this mobisode is 106, even though it was the fifth one released.