Doctor Peterson was a Tau'ri scientist and Atlantis expedition member. During the first year in Atlantis, he was involved in inspecting the storm-damaged parts of the city and was in the same category with Dr. Rodney McKay, Dr. Radek Zelenka and Lt. Aiden Ford. The group arrived and found Dr. Wagner dead with Dr. Johnson dying a minute after. When McKay asked for a containment team, Ford asked why and McKay told him that people didn't just see things and drop dead. He also said that they had spent 12 hours identifying those unexplored parts of the city.
McKay also believed that Johnson and Wagner were the victims of something and that the whole group could have been infected. Zelenka recommended a level-four quarantine which McKay agreed to and informed Dr. Carson Beckett of the situation who along with his medical team left to make preparations. Dr. Elizabeth Weir was informed and she ordered for the city to be placed into Quarantine lockdown. Upon learning of the idea that they would have to stay where they were for the next few hours, Peterson voiced his concerns and regarded it as a terrible idea.
Eventually staying put proved too much for Peterson and he fled from the quarantine, attempting to return to the city despite strict orders not to. He later died, becoming the fifth victim of the nano-virus. He knew as much about the Ancient technology as McKay did. (SGA: "Hot Zone")