Fringe/Recap/S03 E06

Season 3, Episode 6:

6955 kHz
The Fringe team investigate after random people across the country are afflicted with amnesia after listening to a particular number station. Meanwhile, Peter is trying to find out all he can about the Wave-Sink Device, despite Walter's strong objections to his son researching a device that could kill him. During the investigation, the team discover that someone is piggybacking a signal onto the number station. Fringe Division tracks the culprit, who is revealed to be a Shapeshifter working under Fauxlivia's orders: he placed a device within one of the transmitters sending out the number station signal. Fauxlivia kills the Shapeshifter to protect her operation.

Peter theorises that the Shapeshifter was trying to stop people from decoding the meaning of the numbers, so he visits his friend Markham, an old friend who owns a bookstore. Markham gives Peter a book from the 1800s called "The First People", written by Seamus Wiles and describing a technologically advanced civilisation of humans who lived -- and were wiped out -- before the Mesozoic era. The book includes a non-Julian calendar whose numbers correspond with those of the number station. Astrid figures out that the number stations are broadcasting a series of coordinates based on the First People's calendar. When Fringe Division starts digging in the closest set of coordinates (a park in New Jersey), they discover a component of the Wake-Sink Device, leading Walter to conclude that a copy of the device exists in both universes. There are dozens of locations across the planet, and "The First People" book indicates that it was created by the First People and has the power to create and destroy universes.

Fauxlivia contacts Walternate and tells him that the prime universe Fringe Division has begun assembling the device: she's ordered to begin "phase two". Meanwhile, in the alternate universe, Olivia is contacted by Brandon and told that the experiments in travelling between universes has been cancelled. Her apparition of Peter returns, warning Olivia that Walternate has cancelled the experiments because she has outlived her usefulness.