5x2 - Stargate Atlantis

When a mysterious alien organism takes Dr. Jennifer Keller as its host, the newly revived Dr. Carson Beckett and the crew desperately search for a serum to save her from the evolving intruder before it can infiltrate Atlantis. In the meantime, Richard Woolsey officially joins the team, having been chosen as Colonel Samantha Carter's replacement to lead the Atlantis expedition.