Cal Hudson had been assigned as an attaché to the planets within the Demilitarised Zone, a region of space on the Federation-Cardassian border where the colonised worlds of both peoples were forbidden by treaty to deploy armed starships or possess any kind of military hardware. However, many of the civilian human colonists were unsatisfied with the treaty since it involved them giving up much of their land to the Cardassians. Hudson sympathised with the disgruntled colonists and aided them in secretly arming themselves. He joined a group of radicals known as the Maquis, who were determined to take back the planets that Starfleet handed over to the Cardassians. Hudson became one of the group's leading members by 2370 and used his Starfleet position to secure intelligence and supplies for them. Benjamin Sisko uncovered Hudson's deception during the investigation of the explosion of a Cardassian trading vessel and the kidnapping of Gul Dukat. When Sisko and his crew attempt to stop the Maquis from attacking a Cardassian weapons depot, the dogfight that ensues ends in both sides standing down since neither Sisko nor Hudson wish to harm one another, being close friends. Hudson and his group make their escape and Sisko lets them go.
Cal Hudson never appears again throughout the rest of Deep Space Nine's run, but in the fifth season episode "Blaze of Glory", Maquis member Michael Eddington tells Captain Sisko that Cal Hudson was killed in a skirmish with the Cardassians, who were being aided at the time by the Dominion. No further details behind Hudson's death are revealed.