A/N: (I pride myself on having the first fic up after a new episode. Here it is!) If it wasn't obvious already, all the spoilers.
Barry just broke the timeline. That doesn't come without some major repercussions. So! Let's see what they are! This continues immediately after the finale, and will probably end up very long because I need something to do while waiting for next season.
The timeline shattered.
The thing about time travel is that it always bends the timeline. Twists it into a damn pretzel. Some changes are small, and the universe has a way of working around those little curves. Speed bumps, if you like—they cause a minor amount of distress to the driver, but the passenger may not even notice.
Other times, however, the changes wrought are larger. The farther one travels back in time, the greater the likelihood of one of these shifts becomes.
And, in this case, the timeline bent so far that it shattered.
A history lesson:
S.T.A.R. Labs was built by Dr. Harrison Wells in the early 21st century in the middle of Central City. The major accomplishment driving the technological innovation of S.T.A.R. Labs was a particle accelerator.
The particle accelerator exploded worked perfectly, sending waves of dark matter across Central City physicists around the world into excited theorizing about the future. The future brought dozens of dangerous metahumans and a group of vigilantes stopping them vivid and fascinating changes in the world of science. Dr. Harrison Wells was really Eobard Thawne and his wife Tess celebrated their achievement and newfound fame.
Cisco Ramon became Vibe worked alongside Dr. Caitlin Snow and Ronnie Raymond, who died was one of the main engineers of the particle accelerator and so gained secondhand fame through his efforts. Hartley Rathaway was a dick and a villain helped the vigilante team claimed a great amount of media attention, proving a point to his parents.
On a cool night near the end of May 2016, after nearly a year of the particle accelerator functioning perfectly, Barry Allen raced out of a wormhole, wearing a suit that Cisco nobody ever built, back from his trip to the past that never could have happened because nobody ever got powers, dragging Eobard Thawne, a man who had not yet been born, along with him.
That was quite enough paradoxes for one day, thank you, and the universe began to plan its revenge. Quietly. Patiently.
Barry sped down the streets of Central City, motivated by rage and grief. Thawne struggled against him but rage and grief were far too powerful, and Barry kept him firmly in check.
The one thing that gave Barry pause, at all, was that S.T.A.R. Labs looked different. Shinier. Newer.
But why stop to think about it? He'd just altered the timeline. Something was bound to be different.
When he entered the building, zipping through the hallways at Mach 2, there were people he passed, their hair and papers flying wild.
Barry tried to duck into the time vault for a moment to consider why things were different, who were they, none of them were there S.T.A.R. Labs was empty, but the time vault wasn't there.
Because Eobard Thawne was with him and Barry's mother wasn't dead and so Harrison Wells hadn't died and so…
His mind could run a little faster than his legs so he stopped before he could enter the pipeline, and raced back out of S.T.A.R. Labs, sending papers flying again.
An empty warehouse. Barry stopped. Released Thawne.
Thawne raced at him, furious, and without hardly thinking Barry ducked out of the way, pinned him to the wall, set his hand to vibrating before he even realized what he was doing. He paused, mind spinning with anger and grief, and now, finally, a bit of fear.
If his mother wasn't dead, and the particle accelerator never exploded, then there were no metahumans. No metas meant no pipeline to put them in.
If the particle accelerator never exploded, the Flash was never born, therefore nobody knew about Barry's powers.
Nobody but Eobard Thawne.
Barry stopped his hand's vibration. Backed off a little bit. He'd shattered the timeline. The universe was not going to be happy.
"Eobard Thawne," Barry said.
Thawne glared. "Barry Allen."
"I think we need to talk."