Stargate Atlantis S05 E18 Identity

"A new gate will open. A lost city will rise again."

Dr. Jennifer Keller's body is inadvertently taken over by a cunning thief, Neeva Casol. While Neeva tries to escape Atlantis, Keller finds herself imprisoned with a death sentence on another planet, forcing the team into a race against time to return Keller to her original body before she is put to death.