Theory
OUR LIPS ARE SEALED PARTS I & II
You know how Emma's all shocked and shit in the promo? well, my theory is that she's shocked because maybe, it's Sean... and seeing as there are rumors of Daniel returning, I think that can in a way be substanciated. and there's been talk of maybe a secret Semma/Eman relationship, my question is... why would it be secret? Sean and Ellie, albeit unclear, had broken up in Back In Black, so maybe, he comes back and tells her he still loves her...
The only thing I can think of that may be secret is maybe, they elope; which when you think about it, is feesible.
another question is... it's rumored he's in jail for drunk driving, now this doesn't work for two reasons... one, he was off probation in season 3, 2 traffic offenses wouldn't normally incur a jail term, maybe a fine or loss of license, it's highly unlikely he'd go to jail, thus throwing the secret relationship and jail spoiler theory out the window...