Let's begin this recap by running down Claire's (crazed!) storyline from the week. She has Jin and an Other in her tent and seems to be helping the former by tending to his wound. But each time she walks away, the Other tells Jin to untie him so he can kill Claire.
Why? He says he knows her and, basically, she's nuts. But Jin won't do it. After Claire stitches up his ankle - and says she's been in the jungle for three years, but not alone; with her father and with her "friend" - she turns to the Other and threatens him with an axe unless he tells her where Aaron is. The guy says he doesn't know, they never took Aaron. Claire responds by saying they tortured her at some point, branding her and bringing her to the Temple. The guy says she has her facts wrong.
Just when it seems like she's gonna kill the guy, Jin speaks up and says Kate has been raising Aaron. This stops Claire, but only for a moment. She still plunges the axe into the Other's chest. She then turns to Jin, who says he was lying about Kate taking Aaron because he wanted to spare the guy. He can see just how crazy Claire is. Jin says the Others have Aaron at the Temple and he actually saw him there (a lie, obviously).
Phew, Claire says. If Kate actually had Aaron, she says, I'd kill her. Totally freaked out, Jin says he can take Claire to the Temple. The episode ends with someone walking into the tent. It's Fake Locke. Claire smiles and says that's her "friend." Awesome, freaky stuff.
ON TO JACK: In his sideways world, Jack is relatively at peace with his father's death, so he does mention how scared he was of his dad, at least growing up. Jack also has a teenage son he barely sees or gets along with. We never learn who the mother is, though she and Jack live apart.
Jack struggles trying to communicate with his son, David. We (and Jack) later learn that the son is a piano guru. Jack learns about a performance (for entry into a prestigious academy) at the last second and goes to watch David perform. In the audience, he runs into Dogen (!), who seems to recognize Jack and make a point of mentioning something to him about being a father and kids having a lot of pressure on them. Outside the auditorium, David admits to Jack that he keps the piano playing a secret because Jack seemed to "into it" when David was younger.
Jack tells his son he'll always love him and he can never fail him. He doesn't want to repeat the mistakes his father made with him. This segment ends with David and Jack on better terms than ever before.
ON THE ISLAND... Jacob tells Hurley he has to take Jack on a mission. He can convince Jack to go by telling him he "has what it takes," the opposite of what Christian always told his son. This does the trick, and Jack and Hurley are off to... somewhere. They meet Kate in the jungle along the way, who says she's trying to find Claire now.
After a stop at the old caves, where we see Adam and Eve again, Jack and Hurley end up at a lighthouse. Some sort of dial is at its top, which Hurley has been instructed to turn to 108 degrees by Jacob. But Jack sees names/numbers (the same as in the cave last week) and makes Hurley turn to the dial to 23 degrees, his number. The mirror on the dial shows the house in which Jack grew up. This causes him to flip out. He wants to know why Jacob has been watching him for so long. He yells at Hurley. He shatters the mirrors.
Outside the lighthouse, Jack sits pensively and stares at the ocean. Jacob appears to Hurley again and is calm, totally fine with Jack's outburst. It seems to be part of his plan, as he says some people need to figure out their fate on their own and Jack is because he has to do something. But only Jack can figure out what. Jacob also tells Hurley he had to get him and Jack far away from the Temple because someone bad is coming there.