Sam and Dean are charged with a monstrous task: they have to kill Zeus. Yup, that's what I typed. The brothers have to come up with a way to off Zeus. No biggie. In the end, it all becomes another lesson in what someone will do in order to save a person they love.
Gods don't have much luck on Supernatural, do they? Come to think of it, no one has much luck on this show including (or should I say especially) the Winchesters. Remember those side effects Sam exhibited at the end of the last episode? They're getting worse. He's spitting up lots of blood. And, yes, he's not telling Dean about what's happening to him.