"Widow's Sting" is the nineteenth episode of The Avengers: Earth's Mightiest Heroes.
Hawkeye interrupts a meeting between A.I.M. and HYDRA to find the whereabouts of Black Widow. This causes Nick Fury to get angry at Barton for ruining a S.H.I.E.L.D. operation. Iron Man sides with Fury as Hawkeye's revenge is clouding his judgment.
Captain America and Black Panther offer to help Hawkeye to search Black Widow, and they also get the help of Mockingbird, the current identity of S.H.I.E.L.D. agent Bobbi Morse. Hawkeye reveals he put a tracer on Grim Reaper's scythe during his meeting with A.I.M., so he and Mockingbird attack the Reaper but are captured. It turns out to be all part of the plan, with Hawkeye and Mockingbird getting closer to Baron Strucker while Cap and T'Challa closely follow them. Sadly, the Avengers didn't count with the HYDRA transport having a cloaking device.
Hawkeye and Mockingbird are caged, and when Black Widow goes to visit them at their cells, Clint swears revenge against her. When she leaves, Hawkeye frees himself. He and Bobbi are still outnumbered until Captain America and Black Panther manage to track them again and help them. During the fight, Grim Reaper and Viper are captured, but Black Widow escapes with Strucker.
Strucker has a new meeting with MODOK, who tells him A.I.M. couldn't make the Cosmic Cube HYDRA asked for, and will return them the money. Strucker thells Black Widow that MODOK is clearly lying.
At the end, Fury and Mockingbird notice that "Viper" is not actually Viper... she is a Skrull.