Sayid places Sun and Jin's lives in danger while trying to locate Jack, while Jack gets a tempting offer from his captors.
From what I can gather from the guest-starring cast (a lot of Korean sounding names), and the description, it looks like the flashback this time will be related to Jin or Sun (or both) in some way. I'm not sure what the title is referring to. I'm sure that will be made clear, though.
There's a spoiler-filled (maybe bogus) synopsis here:
The Glass Ballerina - Episode Synopsis that may offer some clues, but I won't talk about it in detail for spoilage reasons!

From the previews we know that Ben finds out about the sailboat, so he was unaware of it before. Seems kind of odd that he wouldn't know about it. It's not like its hard to spot a 30' boat or anything! It's only been there, what, three.. four years? Could be they didn't stray far from home until the plane crashed?
Sayid (sorry I've been using the other spelling all this time!) is coming up with a plan to rescue the three captives.
We will go back to Jack, Kate, and Sawyer in this episode. Apparently we still don't get to see what's happened back at the Swan/beach yet. That part interests me more, the conflict between Locke and Eko, and how Desmond plays into that.
We'll see tonight! As always I'll post a review/roundup once its done...
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