Keiller was an old acquaintance of Avon. He was functioning as the purser and security officer of the Space Princess when he contacted Scorpio. When Avon, Tarrant, Dayna and Soolin came aboard the ship, he told them the Space Princess was used to ferry gold from the planet Zerok, posing as a passenger liner transporting fruit, and asked them to help him steal seventeen billion's worth of gold. He explained the gold was processed to become black, making it useless if stolen, and suggested reprogramming the processor.
Keiller stayed behind at the processing centre in secret and was shocked when Avon and Soolin teleported in rather than relying on him to smuggle them inside. He led them to the processing centre but was unable to bluff his way past the guards, forcing the pair to kill them. He was also shocked to learn they had left Tarrant and Dayna to cover their rear without telling him. At the processor, they were ambushed by two men disguised as Zerok security guards and Keiller was knocked out. He was found by Tarrant and Dayna, who took him back to Scorpio. There, they and Vila accused him of hiding something.
Once Avon and Soolin had rejoined them, Keiller claimed someone had blackmailed him over his criminal record and admitted he had been hired to contact the Scorpio crew and enlist their help to steal the black gold, for which he would be paid six billion. Stealing the unprocessed gold was his own idea. He asked the Scorpio crew to take him with them and Avon, who had learned Keiller was previously employed by the Federation as one of Servalan's personal guard, agreed on condition they went ahead with the plan.
Keiller returned to his duty on the Space Princess with Avon, Tarrant, Dayna and Soolin posing as passengers and provided Dayna with a drug to produce the symptoms of exobriddian poisoning. He led Avon to the hold, where Avon killed the guard and Keiller set up a device to fool the security camera. Together, they stole the gold, although Keiller accidentally deactivated the camera device when he was attacked by a booby trap.
Leaving Avon and the gold in a lift, Keiller joined Soolin in his office and monitored the conversations as Dayna's condition was used as an excuse to rendezvous with Scorpio on medical grounds. They went to join the others and Keiller killed Slaten when he tried to raise the alarm. Pursued by guards, Keiller, Tarrant, Dayna and Soolin took the gold aboard Scorpio while Avon covered them, being teleported aboard after them.
At Avon's insistence, Keiller arranged a rendezvous with his employer on Beta-5 and requested a payment of ten million. He waited on the surface with Avon, Tarrant, Dayna, Soolin and the gold but, when his employers arrived, Dayna knocked him down and held him at gunpoint: Avon had guessed that his employer was Servalan and the situation was a set-up. Telling Keiller they couldn't trust him, the Scorpio crew departed with the reward money, leaving Keiller and the gold behind. Servalan told Keiller he wouldn't be leaving Beta-5 and he was killed before she and her guards departed.