WARNING: This article contains SPOILERS for Supergirl & Arrow‘s chapters of “Crisis on Earth-X”

The heroes of The Flash have found a cure for Firestorm‘s powers, meaning the Legends of Tomorrow may lose BOTH members of their team. It’s just one of several bombshells in the Arrowverse crossover spread across four episodes of Supergirl, Arrow, The Flash and Legends. The Firestorm team of Martin Stein and Jax have been struggling to break free of their nuclear bond, and the minds at S.T.A.R. Labs have come up with a solution. The only problem? It will mean the end of Firestorm for good.

That twist may be shocking, but with Victor Garber leaving Legends of Tomorrow this season, it makes a lot of sense. After that news broke, it didn’t take fans long to realize that if one half of Firestorm left, the other would need to go with them. But with no frontrunner for Jax’s new partner emerging, and the cure entering the story of the CW crossover, it seems the time has come.

Is this the end of both Firestorm heroes? Or will the “cure” grant all the powers to Jax?

WHY THE FIRESTORM REQUIRES TWO HEROES

It’s been a long time since Ronnie Raymond and Martin Stein shared a single body as the crazed, uncontrollable Firestorm, and almost as long since the two found a way to peacefully merge and divide, retaining their sanity along the way. The science of that combination has always been more fiction than fact, with the discovery of the ‘Firestorm Matrix’ providing the audience with lasting answers. To make fuzzy science somewhat clear, the same particle accelerator explosion that gave Barry and his friends their powers transformed Ronnie (Robbie Amell) and Martin into a single nuclear being. Divide, and create and explosion. Once divided (thanks to S.T.AR. Labs brilliance), the pair begin a slow climb towards nuclear meltdown, lest they recombine to fuel the Matrix once more.

By now, every fan recalls the saga of Ronnie Raymond, sacrificing his life to save Earth-1 back in season 2 of The Flash and leaving Martin on his own. In need of a new, compatible partner with whom to restore the Matrix, Jax landed the part – and the rest of his time with the Legends of Tomorrow is history. In recent episodes, however, Martin and Jax’s pairing has put a strain on the former. With a child and grandchild to embrace thanks to timeline-alterations, Martin has been looking to leave the role of superhero behind.

THE CURE FOR FIRESTORM MEANS THE HERO’S END

As Cisco and Wells reveal to the Firestorm duo in the first chapter of the “Crisis on Earth-X” crossover, the S.T.A.R. Labs team has put their plan for returning Barry from the Speed Force to a new purpose. For those who may not recall exactly how they did it in the season 4 premiere – and any could be forgiven – it relied on “Quark Spheres,” a theoretical-physics-y McGuffin that would “trick” the Speed Force. These spheres would convince all concerned that Barry remained in his Speed Force prison even after he left. And since the Firestorm Matrix is based on the same kind of pseudo-sci-fi quantum forces, the pair’s research has been repurposed.

The “calm after the Firestorm” as Cisco calls it is effectively a “cure” for the conditions locking Martin and Jax in their symbiotic limbo. Using the same Quark Spheres to fool the Firestorm Matrix into believing that pair’s genetic codes are overlapped (as they would be when sharing a single body) the nuclear threat could be nullified – permanently. Unfortunately for those fond of the Firestorm identity, the cure would make the Matrix self-sufficient and inert. Which means if one of the pair took the cure, that’s all that would be needed to remove the powers from both.

Great news for Martin Stein… but not so terrific for Jax

WILL JAX BE MOVING ON, OR GETTING A NEW PARTNER?

The cure is almost instantly bad news for fans, knowing that Victor Garber’s time as ‘Martin Stein’ is coming to an end – giving this cure more finality than it would usually carry in a world famous for its backtracking, resurrections, and unseen twists. So with Stein destined to leave the Firestorm Matrix behind… what happens to Jax? The episodes do a good job of showing there’s more than just ‘being a superhero’ at stake, given how close Jax and Martin have become while sharing a single form. And while Martin’s first attempts to cook up new superpowers for Jax don’t go all that well, it still remains the most obvious solution to keeping the younger hero in The CW’s Arrowverse. Just… not as a de-powered Spider-Man.

Since Cisco and Wells were able to concoct a mixture to trick the Firestorm Matrix, it seems like a short step to an alternative cure: one which tricks the Matrix into thinking Jax’s form has been merged with Stein’s… allowing Jax to access the powers they would both normally have. Yes, it’s the least exciting solution, and yes, it strays from the very core of Firestorm. But that’s never stopped The CW writers before, and oftentimes, the simplest path is the one chosen.

Although, it’s possible the minds behind this Arrowverse crossover have a surprise in store. Finding a new, compatible partner with which to form Firestorm is how Jax got here in the first place, so the second time may be the charm. Fans are free to throw out their guesses on who could fit the bill, and whether shifting Jax into the ‘veteran’ role would be a welcome change on Legends of Tomorrow.

The crossover continues on The Flash and DC’s Legends of Tomorrow at 8pm on Tuesday, November 28th.