The Arrowverse is headed for a Crisis on Infinite Earths - and the latest episode of The Flash suggested that the series is already setting it up. The CW has already confirmed that the 2019 Arrowverse crossover will be inspired by DC Comics' classic Crisis on Infinite Earths event, with the Monitor warning that an interdimensional threat is coming; the "Elseworlds" event even introduced the Psycho-Pirate, a key villain in the comics.
The Flash has been teasing an impending crisis for years, ever since its pilot episode back in 2014. Eobard Thawne - a.k.a. the Reverse-Flash - possessed a secret Time Vault, and was seen contemplating a newspaper from 2024; the main headline read "Flash Missing, Vanishes in Crisis." Beneath was a second, "Red Skies Vanish." Both of these headlines were deliberate allusions to Crisis on Infinite Earths, where the red skies were a sign of a reality's imminent destruction, and the Flash sacrificed himself to prevent his world being consumed by antimatter. But it seems the Crisis is due to happen a lot sooner than anyone had expected - as soon as this year.
The latest episode of The Flash, "Goldfaced," contained an explicit nod to the coming Crisis. In the opening scene, XS talks to her secret accomplice, Eobard Thawne, and asks for his advice over how to deal with Sherloque Wells. "I can fix this," Thawne observes. "A man... does not wear another man's face unless he understands his mind. Not just through time but across infinite earths." It's the first time the Arrowverse has explicitly acknowledged the existence of Infinite Earths. Until last year's "Elseworlds," it was believed there were only 52 Earths in the multiverse, with the addition of Earth-X, but "Elseworlds" opened with the destruction of Earth-90. There have since been references to alternate Earths numbering all the way up to 221. According to Thawne, however, there are indeed "infinite earths."
One of the greatest minds in the entire Arrowverse, Eobard Thawne - otherwise known as the Reverse-Flash - is a man from the future who hates Barry Allen with a passion. No villain has cost the Flash more; Thawne was responsible for the murder of Barry's mother, Nora, and he's currently working with Barry's future daughter XS. Nora believes Thawne is attempting to stop Cicada, but no doubt he has plans of his own. And here's the interesting thing; those plans will undoubtedly be part of the coming Crisis.
Over the last few years, The Flash has gradually revealed what is written in that future news article. Written by Iris West-Allen, it describes an apocalyptic scene in which the sky turns red, and power outages ripple across Central City. Heroes like Green Arrow, the Atom, and Hawkgirl are on hand, joined by champions from other Earths such as Supergirl. The Flash is caught up in a destructive battle with the Reverse-Flash, with everything ending in a blinding burst of light - and both Barry Allen and the Reverse-Flash vanish. The return of Eobard Thawn in The Flash season 5 is an obvious buildup to "Crisis on Infinite Earths," but now it seems Thawne understands the Multiverse in a way even the Flash does not; he's aware that there are an unlimited number of alternate Earths. Thawne is clearly being set up as a major figure in the 2019 Arrowverse event.
The Flash season 5 continues with episode 14, "Cause and XS", on Tuesday, February 12th at 8 PM on the CW.