Dr. Keller (Jewel Staite) is perplexed by a mysterious new sickness that has affected a number of planets in the Pegasus Galaxy and threatens to kill hundreds of thousands of people. Further study reveals that it is not a contagion but a human engineered protein designed to kill a feeding wraith. Col. Carter (Amanda Tapping) and Dr. Keller realize that someone is intentionally infecting the Wraith's food supplies with no concern for the thousands of human carriers who are dying in the process. Meanwhile, Teyla (Rachel Luttrell) shares with Dr. McKay (David Hewlett) a vision she had in which Kanaan, the father of her child, was trying to send her a message that he is still alive. Now, more determined than ever to find him and the other missing Athosians, she convinces Sheppard (Joe Flanigan) to travel with her to a trading settlement in search for answers. What they find there leads them to startling discovery that no one could have anticipated.