Synopsis
The robot called Arsenal has repaired itself after its fight with the Avengers in Iron Man #114. Now its computer Mistress will send it against its foes again. We learn that the robot and computer were shut down for many years before Unicorn accidentally awoke them in IM#114. Since their maker never returned they assume he is dead and that the enemy they were built to fight must have won. Information on radio channels is confusing so Mistress sends Arsenal to get some subjects she can mind-probe.
Iron Man is back leading the team after his #124-128 where Justin Hammer took control of his armour culminating in the "Demon in a bottle" issue. Falcon, Ms Marvel and Wasp are away on their own business, so the Golden Avenger has got permission from Henry Gyrich to call in Hawkeye, Thor, Wonder Man and Yellowjacket to supplement the team of himself, Beast, Captain America and the returned Scarlet Witch. (Vision has also been sent off on an unspecified errand.) (Hawkeye and Thor weren't in the original fight but the rest including Vision were. Because it was in his mag IM was the only 1 then able to hold his own against the robot.)
Iron Man is worried that Arsenal just appeared in Avengers Mansion sub-basement, and disappeared just as easily. If it got in once then it could do it anytime.
Hawkeye excuses himself from the discussion and Beast follows him out, worried that Clint Barton is still sore about Henry Gyrich throwing him off the team in #181. It does still rankle that he was replaced by Falcon, who is currently in Marvel Premiere #49 solving a murder he failed to prevent.
Hawkeye fires an explosive arrow at a shadow he thinks might be Arsenal, but it's Beast who plucks the arrow out of the air. Tiny Yellowjacket flies unseen past them and they all see a hole in the wall. Clint fires a phosphorescent arrow down a shaft behind the hole illuminating a large area not on the Mansion's blueprint. The 2 head down, followed by Hank Pym.
But Arsenal is lying in wait for them and quickly KO's Beast. The computer detects insect-sized Yellowjacket and zaps him - Hank Pym just escapes through a closing door. Arsenal deflects Hawkeye's arrows, and then ties him up with the titanium cable from 1 of them. It takes them both to Mistress for mental scanning. They believe the superheroes to be Axis agents.
Shellhead also left the meeting after snapping at the others, but they reconvene in the comms room for a video call from Gyrich who puts them in touch with a Defense scientist, Dr Singer, who has uncovered info on Arsenal from WWII archives. The robot was the equivalent of Red Skull's Sleepers, designed to strike back if the Axis powers won the War.
This was part of Project Tomorrow. Dr Singer shows them some archived video footage. And Iron Man recognises the Project's Director as his father Howard Stark. Cap figures that Arsenal has the Mansion in its database from those times, when it was the Stark townhouse.
Injured Yellowjacket has managed to make his way up here and now positions himself before a specially designed amplifier and magnification system to tell them what's happening. Especially that Project Tomorrow is underneath the Mansion. And that Arsenal's captured their friends.
Leaving Henry Pym in the care of Jarvis the butler the 5 Avengers go down the rabbit-hole to find the scientific complex below. And behind them Vision returns from wherever he's been. Mistress sends Arsenal to delay them while she attaches the probes to Beast and Hawkeye's heads. (Beast is still unconscious.)
Vision, ghosting through the ground, meets the robot 1st. But Mistress penetrates his android body with an electric current which sends him screaming back to the surface and into the sky. Wanda hears her husband's cry and rushes to his aid. Wonder Man dashes after her, and finds her gassed to sleep. her hex injured Arsenal before she went down, and Simon Williams leaps to avenge her. Only to be knocked down a deep crevasse.
That leaves the Big 3 Avengers who just now reach the scene. On their chairman's orders Thor hurtles down to save WM and finds an underground stream where his limp target floats. But this stream is the cooling system for the computer, which can control its flow. So Thunder God and ionic human are sucked down a whirlpool until Thor uses Mjolnir to smash through a wall, and they are ejected into Central Park lake. Where they also find the crashlanded Vision.
Iron Man and Cap were left to face Arsenal alone. The robot reveals that he thinks they are Nazis, and is appalled that this version of Captain America would fight on their side. But Steve Rogers tells Shellhead to go destroy the controlling computer. Hoping his companion can hold out without him, Iron Man finds Beast and Hawkeye and destroys the helmets that have been threatening (all this time) to drain their minds. He frees Hawkeye and orders him to take the sleeping Beast to safety. Because he doesn't want any witnesses for what he'll do next.
Hawkeye and his burden see Scarlet Witch hurling hex bolts at the robot who holds the limp form of Captain America. Unfortunately this makes it drop Cap down the chasm. But Thor has returned the way he left and carries Cap back up again. And now it's Arsenal vs Mjolnir and more disruptive hexes.
Back in the computer room Iron Man had recognised the face and voice of Mistress as soon as he met them. He tells her that the War is long over and the Axis lost. He takes off his helmet so she can see who he is. Howard Stark had programmed the computer in the image of his wife Maria, who now realises she has been fighting her son.
Realising now that Howard and Maria are truly dead, and that her purpose no longer exists, Mistress self-destructs. Arsenal blows up too. And Tony Stark is left knowing that he has just witnessed his mother die for the 2nd time.