Canadian-born mutants Madison and Lionel Jeffries both enlisted in the U.S. Army. Madison used his mutant ability as a mechanic, while Lionel used his power as a medic. Both psychologically scarred as a result of war, Madison was subsequently admitted to a psychiatric clinic, the Clinic for Socially Maladjusted Super-Beings. There, he met Roger Bochs, a genius inventor who blamed the world for the loss of his legs. Bochs shared his invention with Jeffries-- a large battlesuit named "Box" in a pun on his name, and the two became friends. Madison and Roger were both recruited by Department H into Gamma Flight, the training division of Alpha Flight, and Madison made it through Gamma Flight before the government suspended funding and closed Department H. Alpha Flight continued to operate independently of the Canadian government, and at one point Madison helped Bochs create an upgraded Box armor after it was stolen by Jerry Jaxon.

Madison aided Alpha Flight in their battle with Omega Flight, ultimately destroying its leader, the robot Delphine Courtney. After this, he became Alpha Flight’s resident mechanic and machinesmith, even devising a version of the Guardian suit for Heather Hudson to wear as Vindicator. At one point, Jeffries confronted his brother, now known as Scramble the Mixed-Up Man, and convinced him to restore his sanity by using his powers on himself.

When Roger Bochs was driven insane after he became trapped within the Box armor, Madison used his powers to alter the Box armor until Lionel could help restore Bochs to health. In reality, however, Bochs' restoration was only temporary, and he again embarked on an insane rampage born of spurned love and declining physical and mental health. Madison was forced to take over the Box armor using his powers to allow himself to phase into in place of Bochs. As the new Box, Madison Jeffries battled Bochs and Lionel, who merged to form the being Omega, and he helped destroy the creature that was once his brother.

Joining Alpha Flight as Box, Madison eventually developed a romantic relationship with Heather, and even proposed to her. However, when former Gamma Flight member Diamond Lil joined Alpha Flight, Madison and Hudson drifted apart. Madison rekindled his romance with Diamond Lil, having known her since the early days of Department H, and soon he and Lil left active duty to pursue their relationship.

More recently, when Alpha Flight was reassembled under the sponsorship of Department H once more, Madison joined the team again, although he no longer used the Box armor or its identity. Unfortunately, he was soon kidnapped by the Zodiac. Brainwashed into becoming one half of the Gemini twins, Madison returned to attack Department H, stealing the powerful Nth Projector and releasing a creature that killed the bestial Sasquatch. (It has been suggested that Madison's Gemini counterpart is Lionel Jeffries, due to its power of transmuting flesh.)

The Zodiac was later attacked by the subversive Weapon X project, who hoped to kidnap Jeffries from them. The mysterious Director, Malcolm Colcord, had Madison further brainwashed, this time into serving them. Within days, much of the operations ran by the Director were facilitated by Jeffries, such as in the use of Boxbots, robots created by Jeffries.

Following in-fighting within the project and an attack by Cable’s Underground, the Weapon X program was infiltrated and crippled. Colcord was nearly killed by turncoat agent Washout, but he was rescued by Madison and, after Colcord persuaded Aurora, the three escaped the Weapon X complex using Aurora's superhuman speed to parts unknown.