Because so much of the series is centered on Jack, his flashback episodes are traditionally the weakest, partly because he wears his heart in his sleeve, partly because we learn less about him as a person in these episodes. This is pretty much the same when we see his story in 'The Hunting Party'. He's under the thumb of his father when it comes time to perform the same kind of miracle surgery that he did on Sarah, who we see in this episode as well. He failed, he took it hard, and in a moment of weakness he kissed the man's daughter. As always, he couldn't keep these feelings bottled up, so he told Sarah, promising to be a better husband, only to find that she, too , had run out of patient with him. Jack may have loved her once, but as she puts it, he will always need someone to fix.
Jack might not like Christian, but the fact is he is a lot more alike him then he would care to admit. In the season 2 premiere, he told Sarah that she'd probably never be able to walk again, and Christian told him that he needed to hold out some degree of hope. Now that he has pulled off a miracle, his ego flares up, and he can't help but gloat, which makes his fall even more devastating.
Now that he's finally beginning to establish his leadership on the island, he faces the worse crisis to date, when Michael takes some guns and locks Jack in the armory while he goes after Walt. Why Michael has decided that he has to act now is hard to fathom; we won't get an answer till the end of the season.
Jack forms a party, aided by Locke and Sawyer (who has sure healed up, considering he was near death less than three days ago) Kate wants to help, but the reemergence of Sawyer seems to have regressed their relationship yet again. Now he's treating her like a child, and she brazenly defies him. Only time the consequences are far more devastating.
But then again Jack's behavior is particularly pig headed. He knows from what happened to the tailies how organized and careful the Others can be. He knows because he dealt with Ethan how deadly they can be. And he has to know after a point that Michael is not on his own anymore. Nevertheless, he keeps charging ahead, arguing all the while.
And than what night falls, we get the episodes high point. They run straight into the bearded man who took Walt (who the writers have inexplicably nicknamed 'Mr. Friendly'). He seems to know as much about them as Goodwin did in 'The Other 48 Days', and this time things are far more chilling. And when Jack, not wanting to let things go, tries to press them, we learn that there are a lot more of them than we originally thought. The speech he gives is chilling, particularly the section where he tells them "This is not your island." He then tells them to give up the weapons they're carrying and walk away, which Jack and the others do very unwillingly.
But Jack's attitude is particularly unsettling. He used to blame himself for his downfalls, but ever since he came to the island, he's been finding scapegoats everywhere. He blamed Locke for the death of Boone; he blames Kate for losing Michael, and now he has a whole other bunch of scapegoats to turn to. He is blind to his own failings. Sayid is conspicuous by his absence--- Jack never even thought to ask him around, even though he might have had a far better way to handle the search. Sayid ends up learning about it from Charlie and Hurley, for God's sake. And when he comes up with his idea to train an army, eh goes to Ana Lucia, even though he knows that Sayid has more experience, and is frankly, more trustworthy than someone who killed a woman the moment she brought her people here. But Jack can not communicate, which is one of the reasons this group of people who could make a decent group of warriors, will never become unified. (It's also the best explanation as to why this potential story never goes anywhere.)
Indeed, everyone seems disconnected. Locke has lost his past because of the hatch. Kate and Jack seem to be moving two steps forward and one step back, Charlie is heading down the path to heroin again, Sawyer seems focused on having revenge than anything else (why else does he look at Mr. Friendly with promises that this isn't over?). and Michael didn't think enough of any of the people he's been on an island with for seven weeks. to ask for help on what otherwise might be a suicide mission. Only Sun and Jin are actually making progress with their relationship, and that's because Jin is willing to listen to his wife (then again, she still is the only person that he can talk to.) Despite Jack's remarks that they need to live together or they'll die alone, this episode seems to demonstrate that's exactly what's starting to happen.
Compared to some of the other episodes this season, ' The Hunting Party' isn't nearly as strong. Part of this is because of the focus of the flashback, aprts of it has to do with the disconnect from later episodes, mostly it's because we are edging up to a mystery but we don't gain nearly as much about The Others than we thought. There's more information here, but we're not getting it.