katikat | Official synopsis of Supernatural's S6

SUPERNATURAL: Season six will be a season of mystery and shadow. Heaven and Hell have been left in complete disarray since the apocalyptic events of season five. And now, monsters, angels and demons roam across a lawless and chaotic landscape. And so Dean Winchester, who has retired from hunting and sworn never to return, finds himself being pulled back into his old life – pulled back by none other than Sam Winchester, who has escaped from Hell. The two reunite to beat back the rising tide of creatures and demon-spawn, but they quickly realize that neither are who they used to be, their relationship isn’t what it used to be, and that nothing is what it seems. Link

Man, I do hope that they won't open another rift between the brothers. After all the rebuilding done in S5, I hoped that Sam and Dean would be finally on the same page again. Oh well, we'll see. But it does sound awesome, doesn't it? And it's a great way to bring back Castiel - hopefully! *crosses fingers*

ETA: And more spoilers in the comments!