“An Origin Story” is episode five of season five of Fringe.
In the previous episode, “The Bullet That Saved the World”, Etta was killed. Peter is going through her things as Olivia sleeps. She wakes after he finds a hidden stash of guns and explosives and starts packing them.
In Manhattan, electricity discharges from the air then Observers and Loyalists arrive. The Observers place a cubical device and a portal opens, with items coming through it, scorching the ground when it dissipates. What arrived is checked by the Observers.
Peter, Walter and Olivia are getting ready to go when Astrid calls. She ran into a fire hazard going after the next tape; a propane tank and a gallon of ethanol. It seems that Walter wanted them for something. Then Etta’s phone rings; it’s Ainu. He didn’t know how else to reach them and they need to meet.
They, and Ainu, arrive at the scorched area. Ainu explains that the Observers are thought to be shipping stuff from the future for the air degradation system they’re building in Central Park. Similar events were observed in France and Egypt where other components are built. This is thought to be the first shipment and more are expected. The resistance wants to destroy them. Ainu asks if they know anything about the Observers’ language, as they have a notebook.
The notebook is from an Observer they have captured. He was caught making notes and measurements yesterday, then the portal activated this morning. Peter has found where the device was and Ainu says the Observer had something like that on him. Peter wants it as he thinks they can destroy the entire corridor.
Peter is trying to assemble the cube in the lab and Astrid isn’t getting anywhere decoding the book. Then has an idea; she tells Olivia that each symbol could have many meanings. She needs to un multiple decryption programs simultaneously and needs a lot more computer power. She needs to call Ainu.
Walter finds Peter and says that if Peter is intent on doing it. Walter thinks they can destroy the corridor. But it will be extremely dangerous. Walter demonstrates; by sealing their end of the wormhole from the future, the other end will be turned into a black hole. They need to use antimatter.
They got some antimatter batons, but still need to get close enough to throw one in. Olivia says Observers and Loyalists will be waiting. Walter thinks if they can use their cube to open the wormhole first, they could destroy the corridor. Peter thinks the captured Observer can help them.
Olivia is worried about Peter; he says they need to have a real victory as the other thing they’re working on could take years. And when they’re successful, he wants everyone to know Etta is responsible for saving the world.
Both Peter and Olivia are grieving, and dealing in different ways. And Peter decides to do something definitely dangerous.