Genre: Mystery

When Peter disappears, Walter seeks solace in marijuana. In that state of mind, he and Astrid babysit Olivia's niece Ella, and Walter tells her a fairy tale of a gentle inventor, a stolen glass heart, a detective looking for true love, and a mysterious group of bald men known as the Watchers.

Two teenagers turn up dead and evidence indicates that shapeshifters have borrowed their forms for some special mission. While the Fringe team tries to track them down, Peter grows increasingly suspicious of Walter's secretive behavior.

When the passengers on a commuter train all die instantly of massive power loss, the team realizes that a time traveler is responsible… and that it may be impossible to apprehend him. Meanwhile, Walter writes a letter to Peter explaining his origins.

A healthy woman dies of rapid-onset cancer in a matter of minutes, and the Fringe team is called in to investigate. The killer has connections to Jacksonville… and Olivia is a potential victim. Meanwhile, Olivia tries to come to terms with her knowledge of Peter's origins.