Warnings: SPOILERS for X-Men: Blue #19 & #20 ahead.

The original X-Men’s departure from their timeline recently caused history to go haywire – something Marvel explains in X-Men: Blue #20.

It’s been five years since All-New X-Men #1 (2013) debuted. In the issue, the modern version of Beast (aka Dr. Hank McCoy) recruited a young, alternative universe version of his Original Five (or O5) team from the past to help defeat a now-extremist Scott Summers. The O5 have been trapped in the present since then but have accepted their place, albeit with a few fish out of water moments.

Hank later used black magic to send the team back to their home dimension. When they arrived, they were shocked to discover that they’d either never left or had been rewritten into the timestream. Clearly, something was still wrong with continuity, because their world began to vanish around them.

The X-Men Engage in Some 'Cross Time Capers'

Written by Cullen Bunn and drawn by Jorge Molina (and a rotating cast of artists), X-Men: Blue kicked off after a dark time for mutant-kind. The X-Men picked up the pieces after the M-Pox scare and the conflict with the Inhumans in X-Men Vs. Inhumans. After Kitty Pride and her team rebuilt their school in Central Park, the time-displaced team took a quieter tact, venturing off on their own.

They headed to the island country of Madripoor and teamed up with their one-time adversary, Magneto – even as he secretly built a time machine to deposit them in their own time. Along the way, they added team members Jimmy Hudson, the Wolverine of the Ultimate Universe (Earth-1610), and Bloodstorm, a mist-vampire version of Storm (don’t ask) from the Mutant X Universe (Earth-1298). But something still felt off, and the classic crew couldn't put their fingers on it... at least until the timestream began to fall apart.

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When people disappear and established events unravel, Jean Grey is hit by waves psychic pain, including telepathic pain from Magneto. He reveals that he's been in contact with Professor X across time. Xavier encouraged him to build a time machine and send the team back home. However, when they use it, something goes wrong, and they wind up in the year 2099. There, they befriend the X-Men of the era while also making a horrific discovery: somehow, their alternative selves built a desolate dystopia.

Their next time-hop also goes awry, sending the squad to the recent past. They realize that the continuity changes are worse, as the world lies in ruins. Emma Frost and Sean Cassidy (Banshee) are the sole survivors of her Generation X class, and, once again, the original X-Men appear to be the cause. They finally make it home, only to discover that their parallel selves have killed the Brotherhood of Evil Mutants and are about to kill young Magneto. What could make them fall so far from their own peaceful vision?

The “Original” X-Men Cause Big Trouble for the Timelines

In X-Men: Blue #19, it turns out the X-Men of the past weren't corrupted, rather a time-jumping future-version of the Brotherhood of Evil Mutants, known as the Brotherhood from Earth-13729. Charles Xavier II, the son of Professor X and Mystique, believe the original X-Men had disgraced his father’s legacy. Together with his half-brother, Raze Darkholme (the son of Mystique and Wolverine), they founded the Brotherhood to set things right, at least according their own warped way of thinking. They culled a mind-controlled team of mutants, including a nasty version of Beast, Ice Thing Bobby Drake, Old Man Deadpool, Bruiser (an alternative version of Molly Hayes from Runaways), and a telepathic manifestation of Jean Grey as Xorn. Phew! Still with us?

Related: How Marvel Will Reveal the Mystery of Wolverine’s Return

In their first encounter, during the “Battle of the Atom” storyline, the Brotherhood masqueraded as O5 X-Men to force them into the past. This time, Xavier the Second realizes the displaced team left a void. He takes his somewhat willing band into the past and impersonates them, creating deep ripples across the timeline – changing the future of mutants for the worse. He also locks his father in a tweaked version of Cerebro, keyed to crush his immense telepathic abilities. However, he’s still powerful enough to send a message to modern-day Magneto, asking for help.

The fab five plus two confront their dupes in their original era, engaging a protracted battle. To uneven the odds, Beast recruits some help from the future, bringing in the X-Men from 2099 and the Gen-X teachers. Together, they defeat the Brotherhood, who escape into the timestream, time-travel jokes and all.

Will The X-Men Finally Go Home?

With the future restored, the X-Men resign themselves to staying in their past. However, it’s not in the cards. Professor X informs them that they know too much and are too different from their previous selves; remaining behind could irrevocably alter history for the worse. Before they can return home, the O5 needs to return to the exact place they disappeared from.

Back in the present, the X-Men realize that, despite continuity returning to normal for the most part, they still remember their temporal hopping. Hank believes their memories mean that they are the “anomalies” to continuity. Presumably, they'll still have to return to their original timeline for good – especially with the New Brotherhood still at large.

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Or are they? After allegedly communicating with Xavier, Magneto tracks down Charles II and his crew in the timestream, preparing for another run on the O5's timeline. He asks Professor X to forgive him, wiping the continuity-wrecking ne’er-do-wells from the timeline. At least, so it appears.

Now, only time will tell when – or if – the classic X-Men can ever truly go home again.

Next: Marvel Comics Finally Gives Quicksilver His Due

X-Men: Blue #20 is currently available.