Dr. Nelson Arroyo was an award-winning scientist with a PHD in robotics. He was also part of the team that worked on Project Zeta.
Nelson Arroyo was the first scientist Zeta and Ro tracked down in an effort to prove Zeta's innocence. By the time they started looking for him, he had abandoned his clandestine work for an ordinary career in Dyron Aerospace. Unfortunately, their attempt to infiltrate the building went awry, and a battle between Zeta and a security drone led to the destruction of his lab. Only later did Arroyo himself arrive, investigating his destroyed laboratory with Agent Bennet, who used the incident as evidence to the doctor that Zeta was still dangerous. Knowing Zeta wouldn't give up trying to find him, Bennett organized a trap for the robot, using the doctor as bait. Later — following an ill-advised meeting with Ro — Zeta met the terrified doctor on his test pad, just off of Marshall Road.
Bennett sprung the trap, surrounding both of them with a steadily shrinking EM field, theoretically placing the doctor in no harm while disabling Zeta. This plan, however, did not account for the pieces of machinery lying around the pad, which the field caused to go haywire, including a container of explosive bolts. When the doctor tried to escape what he still believed to be a killer robot, he ran unthinkingly toward the box, at which point Zeta caught him and shielded him from the ensuing explosion, catching him completely off-guard. The explosion also damaged the equipment being used to sustain the field, creating a hole through which Zeta could escape.
Convinced by their encounter that Zeta had indeed changed, Dr. Arroyo helped Zeta flee in his car, their escape being covered by a group of angry Spaceys. With a safe distance between themselves and the NSA, Arroyo said he would probably be arrested when he returned, but echoing Zeta's words to him earlier, he had done what he thought was right. Arroyo couldn't prove Zeta's innocence, not having been let in on much, but he pointed them in the direction of Doctor Eli Selig, the man behind the project. Before driving away, he told the two to "watch the 'Net", assuring them that they would find him.