In Season 5, Episode 10, Daenerys Targaryen is rescued from the fighting pits by her dragon Drogon, as the sons of the harpy close in on her.
Drogon brings Daenerys to his lair in the Dothraki grasslands. As Drogon is injured and needs to rest, he ignores Dany's please to fly her back to Meereen.
Daenerys is starving and decides to leave her dragon and look for food. This is when she gets spotted and surrounded by the Dothraki horde.