Beware the Widow's Bite is the 19th micro episode of Avengers: Earth's Mightiest Heroes.
In the Cube, Hawkeye is returning from his visit to Bruce Banner catches the Black Widow stealing Bruce Banner's blood sample, and arranging a meet with Hydra out in the desert. He follows her and demands to know what's going on, but she turns the tables on him, and with S.H.I.E.L.D. Agents arrive, she stuns him and claims that he's the traitor. She tells them to take Hawkeye to the Vault, and she will take care of the Hydra agents. After they leave, she contacts someone and tells them that she has S.H.I.E.L.D. convinced that Hawkeye is a traitor, then exclaims "Hail Hydra".