"Don't Tread on Me"
Washington D.C. breaks out in riots as its citizens transform into mad snake people due to Viper's scheme to poison the water supply with a mutagen derived from Slither's physiology. The culprits, Cobra, Copperhead, and Boomslang, return to their Serpent Saucer for a getaway but are caught inside by the Captain and Diamondback. Cobra manages to slip away while claiming (dishonestly) to Diamondback that he's really working as a double-agent for Sidewinder. He spots her Saucer outside and tries to steal it, but Nomad and D-Man are waiting onboard watching the captive Viper. Cobra tries to take the opportunity to assassinate Viper, but thanks to the heroes' interference, his acid bullet hits her bonds instead. Cobra slips away again as Nomad and D-Man get in each other's way trying to stop him. Nomad gets fed up and storms off after Cobra on his own, and just as D-Man wonders if it's even possible to work with him, Viper sneaks up and bites him with her poison fangs before leaving to enjoy the chaos. With Copperhead and Boomslang wrapped up, Cap and Diamondback enter shortly to find the troubling scene of Viper and Nomad missing and D-Man dying. They give D-Man the antitoxin and the Captain tells Diamondback that if she wants to prove herself to him, she'll stay to watch over D-Man while he heads out to look for the others. Diamondback complies, though she's disappointed as all she wants now is to be fighting alongside Cap.
Things quickly go badly for Cap's crew. Nomad is fighting through hordes of serpentine Washingtonians when a sniping shot from Cobra causes him to get overwhelmed. Diamondback is about to leave D-Man on his own to follow after Cap when the government's Captain America and Battlestar show up to investigate the suspicious Serpent Saucers. D-Man rouses himself just enough to throw himself into the ensuing fight, but he and Diamondback are both at a disadvantage against the relatively fresh stooges who don't recognize any of the evidence that they're attacking the wrong suspects. Steve Rogers makes his way to the White House, correctly reasoning that's where Viper would aim to the most damage. She got there ahead of him, mowing down Secret Service agents in the confusion, and got to the already semi-mutated President to administer a more concentrated dose of mutagen to turn him completely into a vicious snake man-monster. Cap gets to the Oval Office amid maudlin thoughts of his previous proud and not so proud visits there, and finds himself in the heartbreaking position of grappling with the berserk serpentine President. Cap does his best to get through to the man the cobra commander-in-chief once was and thinks he's succeeding when he sees him sweating, a sign of his body burning out the reptilian traits. Viper steps in from her hiding spot to complicate the fight, but she bails when Secret Service reinforcements arrive. Cap stays just long enough to verify that the President's mutation wears off, then jumps out the window after her. He finds that Viper was already knocked out by a waiting Cobra, who tries to bargain her for the Serpent Society's freedom and a chance to clean out their headquarters. Cap isn't having any of it, so Cobra drops Viper and slithers off, realizing that his double-crossing of both his recent employers means he's back on his own for the foreseeable future.
Later, the Commission is cleaning up after the crisis and it hasn't escaped their notice that the mystery hero they have to thank is the former Captain America, but they're hardly grateful that he's disregarding their ruling and violating security zones. Fortunately for them, they now have most of Cap's accomplices in custody: Nomad, D-Man, and Diamondback. Meanwhile, at a press conference, the mostly-restored President assures the public that the danger has passed and things are back to normal, though he says so grinning through gleaming fangs.
"Don't Tread on Me"