Twenty years before the main events, Cain operated as a criminal within Gasback's robbery crew. During a bank heist, he betrayed Gasback by shooting him in the face and fleeing with stolen money alongside accomplices, igniting their enduring conflict.

In the present timeline, Cain has reinvented himself as "Mayor Kepler" of Macca City. He funded the city's infrastructure upgrades—including its power plant and a colossal bronze statue of himself—using his share of the heist proceeds. His "newly rich" status manifests in gaudy interior decor and an ostentatious lifestyle.

Fearing Gasback's vengeance, Cain places a $300,000,000 bounty on him, drawing bounty hunters to Macca City. He also insures his statue through Bernardelli Insurance Society, prompting risk assessors Meryl Stryfe and Milly Thompson's arrival.

When Gasback attacks, Cain shelters former accomplices Dorino and Mechio—also betrayers of Gasback. During the mansion confrontation, Cain shoots Dorino and Mechio non-fatally to shift blame, pleading for mercy. Gasback remains unmoved.

After Gasback escapes with the city's power plant, Cain attempts to annihilate Gasback, Vash, and Amelia by missile strike. Nicholas D. Wolfwood intercepts and destroys the missile mid-flight. Cain is arrested alongside Gasback and henchmen.

The character appears exclusively in *Trigun: Badlands Rumble*, with no presence in other *Trigun* media.