The story opens at night in a dock area, as Captain America is attempting to take Roger Gocking, the Porcupine, to safety as a mad sniper fires upon them….
One week earlier: Paul Winston, living under the name Paul Vincent, found himself using his top-secret weaponry to try to fend off a relentless pursuer. It did not work; cornered in an alley and wounded, he was easy prey for the masked gunman who took his life. The next morning, police who arrived at Vincent’s apartment found an AIM uniform on display in the living room. Federal agents Dum Dum Dugan and Rachel "Diamondback" Leighton arrived and took control of the crime scene. Contacting Captain America they inform him that this is the second protected witness murdered in the past week and a blurry photo on a security camera shows the killer to be the Scourge of the Underworld. Evidence points to traitor in the organization leaking the list of protected witnesses to the Scourge; Cap assigns Rachel and Dugan to see to the safety of all other recent witnesses while he will look for the source of the leak….
Only three agents had access to the witness file and Cap gathers them for a confrontation. The guilty man whips out a gun and fires on Cap then leaps out of a window, shouting "Hail Hydra!" before expanding the mechanical wings he was concealing. Cap halts his getaway with a shield throw and carries the traitor down to a rooftop where the baddie kills himself with a poison capsule.
In a secret location, Diamondback is meeting with the third Viper, who cooperated with the SHIELD investigation in issue #9 and is now in hiding. Suddenly the wall explodes and Scourge strides in, casually gunning down the Viper. Diamond attacks him but is unable to do very much because of her head injury. Scourge is not here for her today, so he calmly walks away. Diamond mutters, "Hey…I know you" before passing out….