Fans have long anticipated a reunion between Arya Stark and her lost direwolf, Nymeria (named for the warrior-queen of Dorne). Last night, the event may have been previewed. Check it out below around the 13 second mark.
It's plain a wolf will appear in the next episode and, from the editing and backgrounds, it looks like Arya's in that same scene. Now, the wolf shown is very angry, and Arya looks scared, so I doubt it's Nymeria. This wolf also doesn't look like a direwolf and the fur coloring is different.
That's Season 1 Nymeria on the left below and the sneak preview wolf on the right.
However, if the preview wolf is NOT Nymeria, it seems plausible it finds Arya and threatens her. And it also seems plausible Nymeria breaks out of nowhere and saves Arya.
Then the reunion and hugs.
This is pure speculation, of course, but it seems obvious the showrunners wouldn't preview Nymeria for the first time since Season 1 in a sneak peek. But they do love to tease.
Read more about Arya, Nymeria, and their hopeful reunion here.