Warning: spoilers ahead for the Season 4 premiere of The Flash, called "The Flash Reborn." If you haven't seen it just yet, feel free to check out some of our other articles until you've watched the episode.
Season 3 of The Flash ended on a pretty wild cliffhanger as the Scarlet Speedster himself was trapped in a Speed Force prison from which it was theoretically impossible to escape without another speedster taking his place. As the show is called The Flash and not Team Flash or Central City's Finest, we've always known that Barry would return from the Speed Force quite early in Season 4. The big question has just been how the show would bring him back without breaking a bunch of its own rules about the Speed Force. Well, Barry returned to Central City in "The Flash Reborn," and it took the combined efforts of a big brain trust and one true love to figure out how to do it.
The episode started with Iris leading Team Flash--or Team Kid Flash, as Wally wanted to call it--to protect Central City without Barry around, and she was doing a pretty awesome job. When a samuroid showed up demanding to face the Flash, however, Cisco decided the time had come to yank Barry out of the Speed Force. Iris didn't want to do something that risked the world being consumed by the Speed Force, as would have happened in the Season 3 finale without Barry imprisoning himself, but Cisco believed he had a way.
Apparently, Cisco has spent the last six months working on the sly to figure out a way to bring Barry home without wreaking havoc in the process. In fact, he's been working with geniuses from other shows in The CW's superhero universe, including Felicity and Curtis of Arrow, which rules both of them out as characters who died in the big Arrow cliffhanger ahead of the Arrow premiere on Thursday. (Thanks for that, Flash.) They figured out a way to hypothetically stabilize the Speed Force prison and yank Barry out without unleashing the Speed Force energy on the world.
Cisco brought the Speed Force bazooka out of storage with a few modifications, and he and Caitlin worked together to figure out how to use the "quark sphere," which is apparently a thing. The quark sphere was filled with Barry's unique genetic marker and programmed to track his DNA using the electrical current of the Speed Force. They just needed to track Barry down, pull him out of the Speed Force, then toss the quark sphere into the Speed Force to trick the Speed Force into thinking Barry was still imprisoned.
When Team Flash-less gave the bazooka a try, Cisco seemed to lock onto Barry's signal, but no Barry emerged right in front of them. It seemed like their trick with the quark sphere failed... until Barry popped out of the Speed Force, naked and running 300 miles away from Central City. He was clearly altered by his time in the Speed Force, as he spoke in gibberish and spent his time writing strange symbols over the walls of whatever room he happened to be in. The members of Team Flash did what they could do bring him back to himself, ranging from Cisco and Caitlin playing "Poker Face" to try and recreate when he woke from his coma to Joe giving Barry a shave to Iris making a heartfelt appeal to the man she loves to return to her.
Nothing seemed to work as the clock ticked down to the samuroid's deadline before it would attack Central City, and Iris was feeling pretty helpless until Joe suggested that she have a little faith in addition to all her strength. This motivated Iris to do something quite daring: she gave herself up to the samuroid and told it to take her because the Flash would come back to rescue her. Barry meanwhile was in a cell in the pipeline, drawing more symbols, until Joe came to tell Barry what Iris had done. This was enough to jog his memory, and Barry became the Flash once more, racing after Iris and taking out the samuroid to rescue her. Barry was back.
As it turns out, Barry has no memory of anything that happened between when he entered the Speed Force in the Season 3 finale and when he rescued Iris in the Season 4 premiere, although we can bet that his time away and those strange symbols will have a part to play in the rest of the season. Given the kind of threat The Thinker poses, Team Flash have a lot of work ahead of them.