city of Atlantis, Beckett examines a severed Wraith arm that Major Sheppard brought back from the planet Athos. Beckett can provide the first information about Wraith physiology and becomes the chief medical officer in Atlantis. In "Hide and Seek", he creates a gene therapy that emulates the ATA gene in normal humans with a 48 percent success rate. In "Poisoning the Well", Beckett helps the Hoffans develop a drug that kills the Wraith who feed on humans, but the drug has the side effect of killing 50 percent of the human recipients as well. One of the casualties is Perna, a Hoffan woman he has grown attached to. Carson leaves in disgust when the Hoffans decide to disseminate the drug among their people at all costs. In "The Gift", he discovers that Teyla has Wraith DNA in her genetic makeup, which allows her to tap into the Wraith psychic network in this and future episodes. In the second season, Beckett takes up more offworld activities, including one mission where he removes a Wraith tracker from Ronon Dex's spine in "Runner". In "Instinct", Beckett develops a retrovirus to turn Wraith into humans by stripping the Iratus DNA from them. After the first subject, a Wraith girl named Ellia, experiences the opposite of the desired effect, he tests a perfected retrovirus on a captured Wraith named Michael. Although the experiment works, Michael discovers his identity and reverts into a Wraith after his escape. In the season two finale, "Allies", Michael contacts Atlantis with a proposal to use the retrovirus against rival Wraith hives, but Beckett realizes Michael's betrayal too late. After Michael's Wraith ships are stopped from getting to Earth in "Misbegotten", the humanized Wraith are transported to an isolated planet (M8G-352), where Beckett teaches them how to administer the retrovirus. However, a group led by Michael realize their true histories and capture him. Beckett is later rescued by his teammates, not knowing that Michael has taken a sample of Beckett's DNA. A group of Ancients evict the expedition from Atlantis in the mid season three two-parter "The Return". Beckett is given a surgery post at Stargate Command (SGC) on Earth, but he and some former expedition teammates return to the city to save it from Asuran siege and imminent destruction by the SGC. In "Sunday", Beckett is killed while attempting to safely dispose an explosive tumor that he had removed from