He tried to harness the Omega molecule, the most powerful and unstable substance in the Milky Way Galaxy. He did this to help his people gain much-needed energy supplies. Allos and his team succeeded in producing many millions of the molecule, but the experiment backfired when the containment chamber holding the Omega molecules exploded, exposing the team to deadly radiation and disrupting subspace throughout their star system.
He was rescued by the crew of USS Voyager. While he was being treated, he talked with Seven of Nine about the Omega's containment. He assumed Voyager intended to save the molecules, so he suggested that they transfer the rest to the ship. When she replied that they intended to destroy them, Allos called her blind to destroy his people's future. He was later returned to his people after Voyager successfully destroyed the Omega molecules. (VOY: "The Omega Directive")