The Walking Dead Season 7 Finale: 10 Things That Should Happen
10. Reveal The Inside Person
"A little birdie told me that Rick and the rest of your people are up to no good."
They're the words of Negan to Sasha in the previous episode, which could (and should) have big implications on the finale.
While we've seen Eugene go over to the Saviours and become 'Negan', that was before Rick regained his desire to fight back against Negan's tyranny. So unless he's gleaned it from the sight of Rosita and Sasha at the Sanctuary, which is plausible, then it isn't him.
Another candidate is Gregory, who is definitely the type to rat out Rick, Maggie et al, but he seems to be heading to the Sanctuary after this happens, unless we're seeing the stories operating on slightly different timelines.
Then there's Jadis, who probably can't be trusted and does know Rick's plan, but at the same time this would very much be 'bothering', something they're largely against. Or heck, maybe it's Bertie (you're right to be asking 'who?') because, well, puns and fan theories!
Of course, there's always the chance that Negan is lying to Sasha about this and there is no little birdie, but it's awfully close to the truth for a guess.