"They came from the future. At first, they only watched. Arriving at key moments in human history. We called them Observers. But in 2015 they stopped watching... and seized control. Citizen uprisings proved bloody and futile. Those who survived became known as "Natives." In an attempt to show their allegiance, some Native factions became "Loyalists" and were marked by the Observers. The original Fringe Team fought the invasion, but was quickly defeated. Fringe Division was allowed to continue at a reduced capacity, but only to police the Natives. The resistance was quickly overcome... or so they thought."
WALTER: "They weren't all bad, you know. One of them even tried to help us. He was called September. What happened to him was... unexpected. He told me that in the year 2609 AD they finally ruined the planet. They poisoned it. The air, the water. And when it was fundamentally uninhabitable they traveled back through time and took our planet from us."