Captain America (1968 series) #127

At a SHIELD testing lab, Nick Fury orders Captain America to throw his shield at him. Cap reluctantly complies and his shield bounces harmlessly off of Fury’s new Protecto-Suit. Again, on Fury’s orders, Cap throws a switch releasing a force bolt at the master agent, and again Fury is protected by the experimental suit. Its inventor, Doc Ryder, pronounces it ready for combat situations, and Fury orders it put into production for all field agents. Cap leaves without seeing Sharon and wanders the streets, brooding over his dangerous lifestyle preventing him from having a normal life….

Later that evening, Nick Fury and two of his agents encounter a group of A.I.M. agents but the villains are ready for them: with the press of a button the SHIELD agents’ new Protecto-Suits are nullified and the villains open fire. Fury drives them off with a smoke bomb and heads back to headquarters to find the traitor in their midst. Doc Ryder suggests that Captain America is the only one who hasn’t undergone a security check and Fury begins to wonder if the hero may have been an impostor….

While brooding at home over how he can never let anyone close to him, Cap receives a call telling him his SHIELD security clearance has been revoked, giving no reason. Cap heads for Fury’s apartment to demand answers. Inside, Fury is being questioned by Joe Robertson of the Daily Bugle about the rumors surrounding Captain America’s loss of clearance; the SHIELD boss asks the editor to hold off on printing anything for 24 hours. Outside Robbie runs into Cap but neither is able to enlighten the other about Fury’s decision….

A short time later, Fury visits Tony Stark who is finishing up a powerful android designed to test whether Cap is the real hero or an impostor. Stark is as concerned about Cap as Fury is….

When Steve gets the call to report to SHIELD HQ, he obeys with a heavy heart, bitter over his treatment by long-time colleagues. When he arrives, he is set upon by the deadly new Android X-4 which only the real Cap could escape. The two face off in a trap-filled room and Cap manages to pass the test---but the android’s controls do not work: he can not be shut down. Cap continues to battle the rampaging monster to protect the SHIELD personnel, while Sharon Carter uses a Geiger counter to track the real controller: Dr. Ryder! She tosses a gas capsule into the traitor’s hiding place and brings the captured Ryder back to Fury. When Cap learns that he has been used merely as a decoy to flush out the real traitor, he departs sadly, “I’ve—always been able to be on guard—against my enemies—but how does a man protect himself—from his friends?”