A radio frequency listened by 15 people all over the East Coast transmits a strange signal that triggers their memory loss. They can't remember who they are.
Peter brings Bolivia breakfast in bed along with U2 concert tickets. Walter calls Peter and tells him to stop working on Walternate’s doomsday machine.
The Fringe Division is called in to investigate. The people all suffered from retrograde amnesia and were using short wave radios. They speak to a victim’s husband. Becky was the moderator in a chat room listening to a numbers station. She was trying to crack some secret code.
The Division locates the tower that transmitted the number radio broadcast. They disarm the device, search for prints, and bring it to Walter.
Walter discovers a pulse that is attached to the numbers. The numbers station alone is not responsible. This pulse was to blame for the victim’s amnesia.
Why would someone want to keep the numbers station a secret? Someone must have been close to cracking the code.
The Division identifies the man responsible as Joseph Feller. Feller then sets up another frequency box and a pilot flying a plane accidently listens on the frequency and crashes the plane.
Bolivia and Peter interview a bookstore owner that used to listen to the numbers. He tells them the numbers are very old gives then a book titled “The First People” by Seamus Wiles. The number stations are somehow connected to the first people that ever existed.
Nina talks to Walter and they sit down and smoke a joint. Nina wants to know why he's opposed to Peter investigating that doomsday machine. Walter believes Peter is playing right into Walternate’s hands. Only one world can survive and Walternate will use Peter to make sure it is his own.
Back at the lab, Walter and Astrid read the book. The first people where responsible for inventing the vacuum, a machine able to create and destroy. The numbers code is the key to the universe.
On a frequency box Peter finds a transistor that is newer then the rest. Someone must have replaced it and there are only a few places that sell parts like that and they are all regulated.
Walter and Astrid work on breaking the code by looking for a decipher matrix. Astrid cracks the code. Number stations are a coordination system. The numbers indicate locations, latitude and longitude. They are looking for something buried in the earth in over 38 locations.
Bolivia goes to Joseph Feller and tells him they found the transistor he replaced. The Division track down Feller and Bolivia kills him right before they show up. Feller was a shapeshifter.
The Division begins digging up one location. They find something that is a piece of Walternate's doomsday machine. Could his machine be the vacuum the first people created?
Peter believes there has to be another way, and hopes that one universe doesn’t need to be destroyed.