When the Atlantis team is ambushed by the Wraith on a trip off-world, Dr. Weir begins to suspect that one of the Athosians is actually a Wraith spy. Gate travel is suspended until both parties are separated to different areas of Atlantis. But on their first mission back through the gate, Teyla disappears and the Atlantis team is once again ambushed by the Wraith. With the Athosians secured away from the gate, suspicions rise and tensions increase…could Teyla have been the traitor in their midst all along?