It's Monday, which means there are Game of Thrones spoilers everywhere. Including in this post. So watch out.
If you can remember back to before all the mess at King's Landing, you'll recall that we said goodbye to everyone's favorite eunuch*, Varys. But something fascinating happened before that, in the very first scene of the episode.
The episode opened with Varys writing out the secret of Jon's parentage, presumably to be sent out by raven to everyone in the realm.
He was interrupted by a knock at the door, which turned out to be this little girl — Martha — who reported that Daenerys wasn't eating.
At first, without the context of the rest of the episode, it seems like Varys is keeping tabs on Dany to monitor her sanity. He's aware that she has the potential to become the Mad Queen, but hasn't seen it happen yet.
However, when Varys says to Martha, "We'll try again at supper," she says this:
Why would Martha feel like she was in danger or being watched just for keeping tabs on Dany? With this context, it seems very likely that Varys was in fact attempting to POISON Daenerys, and that Dany (either through luck or on purpose) was evading the assassination attempt by not eating.
This reading of the scene is further supported by a quote from Grand Maester Pycelle alllllllll the way back in Season 1: Ned Stark says that he's heard poison is a "woman's weapon," and Pycelle replies, "Yes. Women, cravens...and eunuchs. Did you know that Lord Varys is a eunuch?"
In context, it seems pretty clear on second viewing that Varys was attempting to poison Dany, so maybe this is all a ~detail~ rather than a ~theory~. But then Martha reveals that Varys has been telling her this:
So, what if — WHAT IF — it isn't Arya or Jon or any of our heroes who ultimately kills Daenerys? This season has been all about subverting expectations...and what could do that more than little Martha fulfilling Varys's command after he's gone?