With the reveal that women who conceive on the island eventually die, the obvious question was how this affected Sun, who was pregnant and not sure who the father of her child was. If it was Jae Lee, she could be safe since it happened off island, but have to face a constant reminder of her mistake. If it was Jin, she could face a death sentence, but possibly experience some peace. Sun had to find out the problem with pregnant women on the island eventually, and Juliet's arrival to the beach serves to give her access to the tools to tell her the truth.
Her thoughts could've been on her time with Jae, but instead they focus on another time she felt coerced into burying a secret, and the cost it took on her and Jin's lives. Sun's major flaw is that she will lie to protect her interests, regardless of who will be harmed in the process. In this episode, to pay off Jin's mother she borrows a large sum of money from her gangster father, who in turn hires Jin to do his dirty work to pay off the debt. Essentially, Sun is responsible for both her and his husband's character flaws.
Unlike the past, her ability to bury the secret of her affair (even if Jin has some idea that it happened) offers a possible road to redemption for her. With Jin being the father, she can completely put her affair behind her, even if that means he has to die for it to happen.
There is one problem that may never be addressed due to the handling of the reveal of the fetus' age. According to Juliet's estimates, Sun's baby was conceived around the time of their estrangement in "…in Translation". It seems unlikely that they would have sex at that time. However, sperm can live for some time after sex, and considering the island's power, it could help survive for longer than on the mainland.
The island's treatment of pregnant women juxtaposes against the fertility of men. Men on the island produce five times more sperm than those off, but if a child is conceived, the mother will die. It's almost like the island has some deep rooted misogyny or adamant opposition to sex.
One of Juliet's purposes in the main camp is the collecting of samples from the women of the camp, particularly Sun & Kate. On that note: what exactly would she get to use as a sample? This adds more to my theory that they wanted Kate and Sawyer to have sex in hopes that she would get pregnant. Considering they are having more sex, Kate's likelihood of pregnancy grows, unless there is some birth control they don't show.
Since Sun was a willing participant, Juliet was easily able to go to The Staff to relay information to Ben about Sun's pregnancy and her status with the other castaways. It's unlikely she would be able to get samples as easily from the rest of the women. However, her willingness to participate in Ben's plan is questioned when she says she hates Ben after she finishes recording her message. This could be reluctance or her venting after playing along for the tape recorder.
While it was the B-plot, the continuation of the search party provided the bigger moments. For starters, Mikhail survived the sonic fence. Obviously it was tough to describe that event in my "Par Avion" review as I try to avoid explicit spoilers of future episodes, even if they aired months or years earlier. Whether the fence was designed to stun a person or wasn't at its full capacity isn't clear yet.
Having Mikhail survive places him in a position to alert the Others to this new arrival. He is also a medic (clearly he didn't spend as much time in combat training as Jin), which allows him to help save Naomi. When she mentions she is not alone in Portuguese, he mistranslates it as thanks for saving her life. This adds some mystery to her and possible ulterior methods for reaching the island.
Desmond's negotiation with Mikhail, save Naomi in exchange for his freedom, is rather controversial. Charlie, who in addition to what happened in the last episode has had several bad encounters with The Others, is obviously the most opposed to Desmond's plan. The brief peace they made in "Catch-22" is dashed in this episode, as they continue to argue over the fateful decision to let Mikhail go.
An element that would've been interesting to explore is Mikhail wearing the Dharma jumpsuit. This would've piqued Desmond's curiosity. This could've been a logical spot for them to explain why he is the only Other who wears Dharma jumpsuits, but sadly, it was never touched upon.
His attempt to take the satellite phone is also a worthy cause of alarm. Obviously, The Others would want that technology, if only to have an advantage over the castaways. It's still not clear if the phone will work again, although Hurley has a little fun talking to "his mom". But having a phone and Naomi both are big advantages for the castaways.
One problem with Naomi's multi-linguistics: why wouldn't she speak English first since that's what they were speaking. It makes sense for Rousseau to try several languages when she was interrogating Sayid in "Solitary", but not here, unless Naomi was so disoriented from her fall and punctured lung that she couldn't make sense out of what they were saying. "One of Us" showed a brief glimpse of news outlets' coverage of Flight 815's disappearance. With the arrival of Naomi, we find out what the rest of the world believes what happened. While it is far more realistic for them to all be dead as the result of the crash, it isn't a confirmation that the characters really are dead and in purgatory, much to the chagrin of those still clinging to that long debunked theory. Instead it implies a conspiracy: someone or something very powerful, like Mittelos, wanted to get these people to the island and to give them enough reason not to look any further. Mikhail not translating properly adds to the possibility that she is on their side.
This episode is another solid installment, setting up the pieces for the conclusion of the season while throwing in a few answers. Once the cliffhanger is seen as something other than an obvious cop out, it adds a new layer of mystery and peril to the survivors. Someone has big plans for them, but who?