SPOILER WARNING: The following article contains spoilers for Marvel's current unfolding Secret Empire event.
This week’s installment of Secret Empire held a number of major revelations regarding both Steve Rogers’ Hydra and the Underground Avengers, but perhaps the biggest and most shocking twist came at the very end when Steve revealed that he has someone inside the Underground itself. While at a glance the team looks to be made up of tried-and-true Avengers whose loyalty couldn’t be called into question, the fact is that we thought that about Steve Rogers himself at one point... and look how that ended up. Furthermore, each of the team has their own reasons for siding with Hydra, whether by choice, coercion or outright manipulation, so we’re going to take a look at each member and the reasons they could possibly be the mole in the Underground resistance.
The core of the Underground is made up of Sam Wilson, Hercules, Quicksilver, Mockingbird, Ant-Man and the AI Tony Stark; all characters with long tenures as Avengers, yes, but every one of them has black spots in their history that could make them susceptible to Hydra’s ways. Whether it’s former bad guys turned good or heroes that have made notable moral lapses in their past, the entire point of the Marvel Universe is to feature heroes painted with shades of grey and any one of them could be the traitor relaying information back to Supreme Leader Rogers.
If we had to pick one person to be the traitor, it’d be Mockingbird without a doubt. In terms of the simplest explanation, Bobbi Morse is an agent of S.H.I.E.L.D., and her allegiance to Hydra could be easily explained by revealing she was present when Doctor Faustus’ brainwashing message went out across the Helicarrier. However, looking outside of the fiction itself, Secret Empire has garnered controversy again and again from the way it's handled fan-favorite characters, and following the end of Chelsea Cain and Kate Niemczyk’s Mockingbird, she’s got a bigger fan-base than ever. Out of all of the people in the Underground, Mockingbird would garner the most online anger, by a mile.
Another reasonable guess would be the AI Tony Stark, who has been shown to be one of the least reliable members of the team, and is often referred to as “inebriated” or “The Drunk” by other members of the cast. Not only that, but considering Hydra was able to hack The Vision and turn him to their side, is there anything stopping it from doing the same to the Tony Stark AI which is likely less sophisticated than the synthezoid Vision, especially while wearing the out-of-date classic Iron Man armor. Lastly, Brian Michael Bendis has been teasing that the AI Stark may be nearing a traitorous turn against flesh-and-blood humans in favor of AI consciousness, so it’s possible the AI came to this conclusion already and made a deal with Hydra to further its own goals.
In terms of who on the team is the most easily manipulated, it has to be Scott Lang AKA The Astonishing Ant-Man. Scott’s a former criminal with a track-record for being unreliable and selfish. Plus, he has a daughter to worry about. Hydra could have easily got to him at some point and coerced him into serving as their mole in the resistance and it wouldn’t come as too much of a surprise to anyone. Also, Nick Spencer recently wrote Scott for a couple-dozen issues across a couple of volumes and obviously has a great affection for the character. While this move might not seem like something someone who loves the character would do, it would raise Scott’s profile big time, and bring him to the forefront of the Marvel Universe in a way that even his feature film failed to do.
On a similar note, Quicksilver has been accepted back into the Avengers family but it wasn’t too long ago (in Marvel Time) that he manipulated his sister The Scarlet Witch into creating the House of M reality which fell down around everyone and permanently damaged the mutant birth rate. In terms of Avengers who are selfish and out for themselves above all else, Quicksilver ranks at number one and he’d do anything if he thought it would benefit himself and his family. Let’s not forget that Hydra has his sister who is possessed by the elder god Chthon. Perhaps if Pietro works with Hydra to feed them information and betray the team, he might see his sister released from Chthon’s clutches. The only reason it probably won’t be Ant-Man or Quicksilver is that they’re the most obvious choices for a heel turn, and few would be genuinely surprised to see them switch sides.
Hercules is a character where it’s difficult to see why he’d make the switch; there’s little in it for him, first of all, and he’s been a loyal Avenger for decades. However, out of every member of The Underground, Hercules is playing the long game in a way the rest will never comprehend. He’s millennia old and will live for millennia more, so on the other hand, it’s not unfeasible that Steve Rogers may have convinced him that Hydra rule is important for the future of humanity in the grand scale. Hercules perceives time differently, and he’s also known for not being super great at making decisions, so he could be the mole in the Underground.
Lastly, we have the former Captain America, Sam Wilson. He’s being presented as the natural opponent to Steve Rogers and his vision for a Hydra America... but what if he isn’t? Interviews regarding Secret Empire have spoke about how it’s about a good man can be corrupted by ideas, but that doesn’t truly track for Steve Rogers, whose history was changed by the Cosmic Cube. What if, instead, that good man is Sam? Solicits for future issues of Captain America show them coming to blows, so he’s the least likely candidate, but there’s always a chance he'll be the hero to make that unexpected heel turn.
Ultimately, it could be any of these characters, for any number of reasons. One thing is for certain -- we won’t have to wait too long to find out thanks to the event’s hyperspeed publication schedule, so we’ll have the answer sooner rather than later.