Arlen was a Federation officer who infiltrated Blake's operation on Gauda Prime. She first approached Blake at his campsite in the forest where he noted she was carrying a Federation weapon and wondered if she'd been issued it. Arlen told him she was being pursued by bounty hunters and offered him her gun as payment for the food he offered. When three bounty hunters appeared, Arlen killed two of them but was wounded by the third, Tando, who was then killed by Blake. Blake then aimed his gun at Arlen, revealing he was a bounty hunter as well.
Blake took Arlen back to his flyer, telling her his name. He took her to his base and handed her over to Deva. Arlen offered him information on Blake in return for her life. She passed the test Blake had set with the bounty hunter charade, being accepted into his secret rebel group, and was uniformed as a guard when Blake brought Tarrant in. When Tarrant escaped, Blake stopped Arlen shooting him as he fled, convinced he'd join them when he learned the truth.
When the Scorpio crew attacked the base, Arlen accompanied Blake in meeting them and witnessed Blake being killed by Avon. Deva entered to reveal they were under attack from the Federation but Arlen promptly killed him and ordered the Scorpio crew to throw down their weapons, declaring her loyalty to the Federation. (She insisted on being called an officer when Tarrant called her a Federation agent.) Vila approached her pleading innocence and Dayna used the distraction to retrieve her gun but Arlen fired first, killing her. She was then knocked unconscious by Vila. (D: Blake)