"Fire + Water" is the twelfth episode of season two. The flashbacks are all about Charlie and the piano that was given to him as a child, which his brudder Liam sells for drug money instead of being a father. Also they do an awesome commercial for nappies. That's British for "bad idea."
So this episode sort of really sucks for Charlie, who is only trying to do good things but then Claire slaps him because he sort of stole a baby.
Kate is helping Sawyer do his "I got shot and Jack fixed me" exercises, when they see Jack and Ana Lucia walk out of the jungle. Sawyer makes a (WHAT A SURPRISE) sarcastic comment about how it's the third time they've walked out of the jungle together and that Jack's probably giving her the WINK WINK, NUDGE NUDGE I'M AN ASS "20 dollah toor". Kate, uh, listens? And then tells Sawyer to keep doing his "I got shot an Jack fixed me" exercises.
Laterz, Jack is helping Ana Lucia build her shelter, and Ana Lucia wants to know what made Jack turn back after his Mission Abandon Michael
succeeded failed. Jack says point plank, "They had a gun at Kate's head."
Ana's a little surprised, and in her whutiztact way, she asks if Jack is hitting that ass. Jack is shy/embarrassed, so Ana explains:
"Plane crash, you both survive...nice beach... She's hot, you're hot, it's what people do."
Jack is sort of grinning the whole time, and then he laughs and goes, "I'm not 'hittin' that'." All is made of win.
The rest of the episode is about Charlie slowly losing it but having a good heart, and being totally messed up. Poor guy. Jack kind of takes care of Charlie (including sewing him up), while Kate does some business protecting Claire from him.