21. Northwest Passage

Complete story — includes the ending

Peter travels to a small town and gets involved with the disappearance and murder of a young woman, Krista, after she made plans to meet him but never showed up. Initially, the police suspects Peter was involved in the disappearance, but Peter decides to aid them in the investigation after catching a glimpse of Newton, believing the shapeshifters are responsible and are coming after him; however, he does not wish Walter to be involved. Later, town Sheriff Mathis ( Martha Plimpton ) notices her partner is missing. After they go to the scene of Krista's murder, Peter encounters Newton, but they get away. Peter begins to doubt the shapeshifters' motives after another body is found, but eventually comes up with an idea to read and track the victims' adrenaline spikes, which allows him to find where the murders took place; a dairy farm. They find the owner, who confesses to killing the women because they rejected him, and to kidnapping and torturing Mathis's partner when he discovered the culprit. In the end, Peter decides and prepares to head back to Boston, but is approached by Newton, who has brought "Mr. Secretary", the man from the Other Side, to see Peter; the man is his actual father from the parallel universe, "Walternate".