A young man named Nathaniel Richards wearing armor came from the future fleeing Kang the Conqueror. He arrived at Avengers Mansion, but it was abandoned in light of the Scarlet Witch's mental breakdown. He headed to Stark Industries, and he was able to access the A.I. of Vision and uploaded it into the armor.
The A.I. explained that it contained the Avengers Fail-Safe Program, listing young heroes related to the Avengers
He formed a team with Eli Bradley, Billy Kaplan, and Teddy Altman. They took every mission available, such as rescuing people during a fire. After their first mission was recounted in the Daily Bugle, Jessica Jones was sent to investigate the heroes who had been nicknamed Iron Kid, Lieutenant America, Teen-Hulk, and Thor Jr.. Captain America and Iron Man also investigated.
Cassie Lang was interested in following her father's legacy, and her powers accidentally triggered during an argument with the others. Kate Bishop accompanied the heroes after helping them fight off kidnappers at her sister's wedding.
The Young Avengers prepared for Kang's arrival. Captain America, Iron Man, and Jessica Jones tried to dissuade them, and had them locked in the Mansion while they awaited Kang. Kang was able to convince Cap and the others to assist him in this effort, showing them visions of an apocalyptic future he claimed would occur if Iron Lad was not forced to become another version of Kang. Kate had memorized the access codes, though, and was able to let them out as well as find items for them to prepare to battle Kang.