Much of Madison's past is unknown. He and his brother served in the US army during Vietnam. Madison worked as a mechanic, Lionel as a medic. While Madison had been uncomfortable with his powers, Lionel seemed to relish using his. Their unit was heavily damaged after a mission and Lionel seemed to go insane. He used his powers on the dead and wounded with horrific results. Madison had to use his powers to restrain his brother and had him committed.
Madison was apparently recruited by Guardian and was part of the Gamma Flight training group. He became romantically involved with Diamond Lil, also part of Gamma Flight. Madison's first major action was to dismantle Courtney Delphine when Omega Flight attacked Alpha Flight.
Madison worked on a new version of the Box robot with Roger Bochs. He was able to find or make a special type of living metal that allowed the operator to merge into the armor rather than control it via remote. Bochs and Jeffries then both officially joined Alpha Flight. When Bochs started to go insane, Madison took possession of the Box robot. With his powers he could form weapons and devices to augment it as needed.
While James Hudson was presumed dead, Madison and Heather became close, and even became engaged. However, he continued to secretly see Lillian and eventually realized that he loved her and not Heather. He also helped James Hudson when he was captured by Roxxon.
Heather began looking into Madison's past and discovered his brother Lionel in a mental ward. Madison knew his brother was a danger and tried to stop her. Calling himself Scramble, Lionel escaped and set up a 'clinic' where he would work on others, claiming he could fix any ailment. Bochs was one of the ones who showed up, wanting legs. The two then merged into Omega, wanting to use their combined powers. Although Persuasion was able to briefly separate the two, Scramble lobotomized Bochs and reformed Omega. Madison felt that his brother could never be rehabilitated, so he formed a large cannon and destroyed Omega.
He and Diamond Lil retired and married. Lillian attempted to keep him from using the Boxbot. Madison finally admitted he was becoming addicted to using it, as well as being an adventurer.
He still rejoined Alpha Flight after it was reinstated by Department H, although his wife asked him not to. However, she was able to convince him not to use Box unless it was absolutely necessary. On a mission with the team, Jeffries was knocked out battling the Zodiac. They brainwashed him into being Gemini and had him create a robot duplicate to control. Despite Puck finding and unmasking him, he seemed to still think Alpha Flight were his enemies.
Jeffries was then taken by Weapon X. He was manipulated to think that Director Colcord is his ally and not to question what the intended use of his projects are for. He is working on a new generation of Sentinels as well as using Box robots to keep the Neverland prisoners in line. He may not even realize that his wife Diamond Lil is one of the detainees in the camp. With Neverland now being abandoned, Madison and his prototypes accompany Colcord.