BuddyTV reports the twist to end Season 3 of Lost will center around our favorite tatooed doctor, Jack. 

FTA:

In the magazine, co-executive producers Edward Kitsis and Adam Horowitz, are discussing an unprecedented third Jack flashback.  Whether or not the entire flashback belongs to Jack or not, is unknown, but in discussing it they let slip that Jack is at the center of ‘The Snake in the Mailbox’.

“…we haven’t been this excited since we decided at the end of season one that Walt would be taken.  This is Top Secret.  It’s so secret that there’s a codename — ‘The Snake in the Mailbox’.” 

As you probably remember, Season 1 ended with Walt being abducted by The Others (with the first appearance of Tom a.k.a. Zeke a.k.a. Mr. Friendly).  In the Season 2 finale, the last we saw of the island folk was Jack, Kate and Sawyer being, again, captured by The Others.  It’s admittedly tough to establish a trend after just two occurrences, but I’m going to do it anyway.

Jack will officially join the others.  All season long, he has been becoming the “Christ figure” for the rest of the Losties, by joining and helping The Others to save his friends.  He’s becoming one of them.  Heck, he’s playing football with them.  But his tatoo (which we’re supposed to be learning more about eventually) apparently reads “he walks among them but isn’t one of them”.  That will change when he gives himself completely over to The Others.

Oh, and here’s your grain of salt.  Enjoy.