In the pilot episode, Mike is seeking work after being laid off from his job. He is concerned with how he will provide for his son, Ace. After having subjected himself to the Centipede Project, an organization for the furthering of the Extremis serum, he is given an implant on his arm that provides him with extreme strength. An explosion occurs in a nearby building while Mike is spending time with his son. He uses his power to rescue a woman, leaping from the sixth floor to the street below. As he becomes angrier, his blood becomes more unstable. This would cause him to explode like the man who caused the earlier explosion in the lab. He becomes irate and kidnaps Skye to save her from the "men in suits". He takes her to the train station where Agent Grant Ward shoots him with the Night-Night Gun designed by Fitz-Simmons. Mike is saved just before he explodes.
He appears again in "The Bridge", where he is brought in as back-up for Coulson's team, as they fight against some of the Centipede Project's other test subjects who are even more powered with more centipede implants. He still has his strength as a result of the dendrotoxin, which kept him from exploding. While he was training at a S.H.I.E.L.D. facility, he did not visit his son because he regretted the way he acted at the train station, the last time his son saw him. Raina, a recruiting member for the Centipede Project, kidnaps Ace and sets up a trade-off with Mike between the boy and Coulson. After the rendevous on a bridge, Mike leaves Ace in safety with Skye and charges at Raina and the enemy super-soldiers. Some equipment on the bridge explodes and kills Mike Peterson in its blast.
At the end of "The Magical Place", it is revealed that Mike survived the blast. He awakens in an empty room. One of his legs has been amputated and one of his eyes has been replaced by one of the kill switch eyes that Akela Amador had.
In "T.R.A.C.K.S.", Mike became known as Deathlok.