In "Pilot", Ace is with his dad when the lab explodes. He is left behind as his dad enters the burning building and watches as Mike leaps down with the survivor of the explosion. The two leave the scene to avoid blame or capture. As his father becomes more hostile due to the effect of the Centipede serum, Mike takes Ace with him to "save" Skye. After Mike has been neutralized by the S.H.I.E.L.D. agents in the train station, Mike is taken to stay with his aunt while his dad is being rehabilitated.
In "The Bridge", Centepide kidnaps Ace and uses him as a bargaining chip as to force Michael Peterson to bend to their will. After the S.H.I.E.L.D. agents exchange Coulson for Ace, the Centipede agents trigger an explosion which seemingly kills Mike Peterson in front of his son, but Ace is returned to his aunt's house.
Later on, Mike (after becoming Deathlok) reveals that Centipede uses a live video feed of Ace in a locked room as motivation for Deathlok to work for them.
In "Beginning of the End", Ace is found by Skye in the Cybertek headquarters, where he has been held captive and released along with other prisoners. Mike refuses to see his son yet because he has become a monster with his robotic prosthetics.