Synopsis
The Avengers (Captain America, Iron Man, Scarlet Witch, Thor, Vision and their house-guest Mantis) confront an intruder who has KO'd Jarvis to reach a time capsule they have stored. As they try to apprehend him the guy claims Cap is a fake, and casts off his outer garments to reveal a yellow costume. He moves at super-speed and calls himself the Whizzer. (But he's obviously too old to be the villainous Whizzer of the Squadron Sinister from Avengers #69-70 and Defenders #13-14.)
The speedster manages to plough through or avoid most of the Avengers. But when he tries to smash into Vision the android goes intangible. And Whizzer stuns himself against a wall.
Cap realises this man is old enough to be the WWII Whizzer who fought alongside the replacement Captain America in the All-Winners Squad. (That replacement Cap resurfaced in CA#153-156.) Cap and the recovered Whizzer now realise why they don't know each other.
Whizzer confirms all this with a potted history of the AWS. Cap and the replacement Bucky, the android Human Torch and Toro, and Sub-Mariner joined together with Miss America and Whizzer after the War. He says they only had 3 adventures. The 1st was against Isbisa in All Winners #19. The 3rd was against Future Man and Madame Death in AW#21. (There never was and AW#20, and Roy Thomas here posits a missing 2nd tale of the Squad.)
Whizzer reminds them what happened to Cap, Human Torch and Sub-Mariner, who all dropped out of sight at the end of the 40's and then reappeared briefly in the mid-50's. He assumes Cap knows about his own history. Sub-Mariner just spent his away time in Atlantis. Torch's return in Young Men #24 explained that criminals had buried him in the desert in 1949. But Whizzer doesn't know where HT went after the 50's.
He does give us new information about the fate of himself and Miss America. Bob Frank and Madeline Joyce got married after the Squad. They revealed their identities to the US government, and became super-guards on the successor to the Manhattan Project. In 1949 they survived a nuclear accident.
All during his speech Bob Frank has been sweating and his pulse is racing. With a sense of urgency he skips forward to the present, where he heard about a building collapse where the Avengers found the time capsule. Which now bursts open releasing a large figure glowing with nuclear radiation, who Whizzer claims is his son.
Leaving Scarlet Witch to look after the ailing old hero, the other Avengers attack the newcomer. Even though he doesn't really seem to want to attack them. In fact he seems more like a confused child. Despite that he easily defeats them all. And then disappears in a blinding glare and through the wall.
The team scan the city for high levels of radiation, but find 3 sources. So we have a typical split into sub-teams scenario. Iron Man flies off in 1 direction with Cap, Thor takes Mantis, and Vision flies alone. Meanwhile Whizzer has had a heart attack, and Jarvis has sent for a doctor.
Vision finds the glowing monster in an electric power plant. As he often does, the android comments on what he's doing, and uses the phrase "nuclear nemesis". His opponent echoes this several times, as "nuklo nemsiss". But their confrontation is cut short when Vizh ghosts his arm through the atomic body. The monster obviously doesn't like this and flees from the hero. So Vision starts to herd him back to Avengers Mansion.
Thor and Mantis also find a nuclear being on an elevated railway near Coney Island. This 1 too is shouting "nuklo nemsiss", and Thor takes Nuklo to be his name. After being hit by a train Nuklo cringes away from Thor's hammer, and he too is forced to retreat back towards the Mansion.
Cap and Iron man find a 3rd copy of the being shouting "nuklo nemsiss" and tearing up power lines. This time he's afraid of IM's repulsor rays.
Meanwhile the recovering Whizzer tells Wanda more of his story. Madeline was pregnant at the time of the nuclear accident. And her child was born glowing with radiation. The government put him in suspended animation in the time capsule, and buried it beneath a government building. The capsule was set to keep him asleep for 25 years. Maybe by then the baby's condition would have improved, or he could be treated. But that time is up now.
After this the pair went travelling in Europe, and Madeline fell pregnant again. As her time approached they took refuge on Wundagore Mountain and met the High Evolutionary. With the evolved cow Bova as midwife she gave birth to twins. And Scarlet Witch guesses their names were Pietro and Wanda. Bob Frank is her father!
Whizzer admits that he left the twins behind when his wife died soon after childbirth. And after some irrelevant chat about her history with Magneto and the Avengers, Wanda tells us the news that she and her brother Quicksilver grew up on Mt Wundagore, but ran away when they were teens.
By now the 3 teams of Avengers have driven the 3 Nuklo's back to the Mansion, and the 3 beings meet in an alley and fuse together. The electric power each has absorbed means that the combined Nuklo is even more powerful than before. Again he is too much for the Avengers.
But Whizzer hears the battle, and rushes out carrying Scarlet Witch. She surrounds her new-found brother with a hex sphere. Nuklo expends all his stored energy trying to break out, until he collapses drained. Wanda claims that it was their shared DNA (but not in those words) which enabled her power to cancel his.
Later Tony Stark devises a new stasis chamber for Nuklo, and Don Blake performs an operation to save Whizzer's life.