One of the things the passengers of Flight 815 is that they all seemed to have parents whose lives were an added burden to them. Locke's father was a con man; Jack's was a drunk; Sun's father is a criminal; Sawyer's mothers affair ended in tragedy. This season we've seen how Shannon's stepmother and Ana Lucia's mothers coldness severely damaged them as people. But now it seems that the person with the most damaged parents is Kate, which led her to finally commit the crime that led to her original arrest. And based on that, hers may have been the most damaged of all.
Kate's mother was a battered woman, abused and beaten down from the man Kate thought was her stepfather. There are also suggestions of molestation. Kate finally kills him in an effort to bring some peace to her mother. And what does Diane, her mother do? She calls the cops the minute her daughter tells her what she's done. Worse, Kate has learned that the man she thought was her father --- Sgt. Sam Austen (we'll be seeing him again soon--- wasn't her father; the drunken abusive stepdad was, and though he wanted to kill him, he didn't have murder in his heart.
All of this is revealed in a series of revelations that come about when Kate sees a black horse on the island. And based on what we see, that horse is the same one that helped her become a fugitive for the first time. The question is, how did the horse get here? If it is the same horse (and given the ghosts that Jack, Sawyer and Sayid have seen, I'm not prepared to rule it out) is it here to symbolize Kate's guilt or to help her make peace with what she's done? The fact that Sawyer sees it himself at the end of the episode doesn't make the question meaningless. After all, maybe its a symbol for him too.
More important is the ghost of Wayne, who seems to be speaking through Sawyer, and tries to choke her early on. Kate reveals every time that she sees Sawyer, she is reminded of the man she hates, and it disgusts her. But it's clear that she's still drawn to him. It's significant that Kate kisses Jack for the first time, and them immediately walks away--- she doesn't think she's worthy of him, even though Jack is as conflicted as she is.
While the episode largely focuses on, well, 'What Kate Did', we do see quite a bit of some other character, and a lot of time in the hatch. Michael is getting his second look at this place (he really just passed through in 'Collision') and being an architect, he notices the blast doors that are supposed to lower if there's some kind of explosion. Locke brushes off their significance, but they will turn out to be a vital part of his time in the hatch, though we don't know it yet.
Far more interesting is a conversation between Eko and Locke, which is one of the highpoints of the season so far. Eko gives his longest speech so far on the show--- the parable of Josiah from the bible, and hsi discovery of the Old Testament. It is a lofty telling, and does engaging, especially when he hands Locke a bible, which Locke opens and finds another segment of the orientation film that we saw near the beginning of the season.
The scene is significant not so much because of any new knowledge that we gain (its actually a bit anticlimactic) but because it demonstrates the real difference between these two men of faith. At one point, Eko asks Locke if he knows the story, and Locke says he doesn't. This is a man who can recite the most obscure anecdotes about history and nature, but doesn't know a thing about a passage from the bible. He has faith, but it is not religious. Eko's would seem to be the more holy of the two, but look what happens while they are splicing the film together when Locke raises the issue of what has happened. "Do not mistake coincidence for fate," he answers. We don't know what motivates Eko (we're going to find out very soon, however) but he may not believe some of the gospel that he preaches--- at least not yet.
On the beach, Sun and Jin are having a joyous reunion, but Sayid is dully picking up the remnants of his life as he buries Shannon. He is haunted by her, and will be in mourning for the next few episodes. One can't help but feel for him--- after all, Sayid has done an awful lot to help the survivors, and he hasn't gotten much in the way of thanks.. Both Jack and Locke look to him for advice on certain things, but they have a habit of ignoring his advice when it suits them. When people moved from the beach to the caves, it was a blow against the majority, but eventually everybody seemed to move there (now they're back on the beach, but it's not because of anything Sayid has done ) Charlie has made an effort to help Sayid, but mostly he just gets in his way, when Hurley learned which side he fought for in the Gulf War, he recoiled liked the man smelled bad and even though Michael got a lot of help from him building the raft, he didn't offer him passage off, which would've seemed at least partly fair. Sayid is outsider, and he's feel it, though it will take another outsider to make him realize his place.
The most shocking part of the episode occurs in the last minute, when Michael, doing exactly what Eko and Locke are being warned against doing in the next room, finds out that his son may still be alive. Michael doesn't stop to think for a minute whether he's being played, he just keeps steamrolling ahead, as he always does with Walt, and because off that attitude, his actions will bring even more hardship to everyone else.
'What Kate Did' is all about ghosts, both real and imagined Everyone may have wanted a blank slate, but their ghosts have followed them here (though only sometimes in corporeal form). Kate thinks she's exorcised part of her demons, but she hasn't. And even when she gets rid of the ones she brought, new ones will come to replace them very fast.