WARNING: The following article contains spoilers for The Flash #751, by Joshua Williamson, Christian Duce, Luis Guerrero, Hi-Fi and Steve Wands, on sale now.
Over the past few months, The Flash has encountered a dangerous new villain named Paradox, and he's an incredible threat to the Fastest Man Alive. The villain, who came into his powers the very night Barry Allen was struck by lightning, spent some time locked up in prison in the 25th century, before escaping to the past. Now, Paradox has made it his goal to put down the Flash for good. After all, Paradox's powers are connected directly to the timeline since he absorbs the energy created by all paradoxes. Every time there's a change in the timeline, Paradox feels it, and he's felt the ramifications of Barry Allen's actions on multiple occasions.
In The Flash #750, Paradox finally revealed himself, and their subsequent battle has stretched into The Flash #751. After Paradox quickly proves his superiority, the Flash doesn't stand a chance and he is summarily defeated and knocked out. When he wakes up however, he's not where he once was. Instead, Barry seemingly finds himself reunited with his mother, Nora.
Nora Allen was killed when Barry was still just a boy, murdered by his longtime enemy Eobard Thawne, the Reverse-Flash. The loss of his mother weighed heavily on Barry for a long time, and he even used his powers to travel back in time and save her life, an act that ended up creating an entirely new timeline in Flashpoint. The only way to set things back to normal, unfortunately, was to ensure that his mother would die in the past.
Still, that doesn't explain the events of The Flash #751. After the Flash is beaten unconscious by Paradox in the middle of Central City, he wakes up in a beautiful field. Surrounded by flowers, green grass and a luscious, tall tree, Barry notices that he is no longer in contact with Iris because he has no connection in his communication device. Then, when he turns around, he is shocked to see his mother, Nora Allen, who tells him: "Hi Barry. You don't have to run anymore."
There are a few possible explanations at what is happening here, and none of them are good. The first possibility is that Barry is dead, and he is now in some sort of afterlife. This could be backed by the fact that Paradox was so powerful that he was easily able to defeat the Flash. If he didn't hold back, then he may have been able to kill him, sending Barry in some sort of heaven.
Alternatively, Barry could have just woken up in the Speed Force. There is precedent for this given that, in The Flash television show, Grant Gustin's Barry Allen once found himself trapped in the Speed Force, whose sentience had taken the form of his mother to interact with him. Given that the Speed Force has played an important role in recent comic book storylines, it's possible it could now reach out to him in his moment of need.
Finally, Paradox could have somehow sent Barry back to the Flashpoint timeline -- the alternate reality where his mother was still alive. While the Batman/The Flash crossover story "The Button" saw the Flashpoint reality get erased from existence, Paradox may have been able to recreate it in some fashion with his powerful abilities. Given that the Flashpoint reality is essentially the biggest paradox Flash ever created, this could end up being connected to the villain who bears the same name.
Whichever situation turns out to be the case, Nora's welcome hints that this is the end of the line for Barry. However, the speedster will have to find a way to race back to his home reality if he has any hopes of stopping Paradox once and for all.