Since The Flash introduced the element of time travel to the series, the storylines have gotten a little complicated. The unstable singularity created by Barry’s (Grant Gustin) trip back to save his mother left behind cracks in time and space that connect to an alternate reality on Earth. Those rifts have brought over a doppelganger Harrison Wells (Tom Cavanagh), an alternate Flash named Jay Garrick (Teddy Sears), and a powerful villain named Zoom (Tony Todd) -- who is faster than any speedster in either universe.
Barry already had an enemy with the same particular skillset, the Reverse-Flash, first known as the blur of yellow lightning that killed Barry's mother. Though originally thought to be Harrison Wells, it turned out that a stranded metahuman from the future had merely adopted the murdered Wells' image. The time-jumping Eobard Thawne (Matt Letscher) was only defeated once his distant ancestor Eddie Thawne (Rick Cosnett) killed himself, thus erasing Reverse-Flash from existence.
Sneak peeks of upcoming episodes from The Flash season 2 include the introduction of Killer Frost, the Earth-2 metahuman version of Caitlin Snow (Danielle Panabaker). She'll be side-by-side with the alternate reality Ronnie Raymond (Robbie Amell), who has lived to take a darker path and become Deathstorm. Entertainment Weekly has snagged the first images of Caitlin and Ronnie's Earth-2 counterparts, so check them out below:
Deathstorm and Killer Frost aren't the only familiar faces that are going to show up, though. A promo for the second half of season 2 of The Flash revealed that the Reverse-Flash would be making another appearance in Barry's life. Considering his rather final end in the season 1 finale, most conjectured this new Eobard would be from Earth-2. However, EW reports that this is the actual Reverse-Flash we are already familiar with. Showrunner Andrew Kreisberg explains that time is not linear on the show:
"Sometimes you've seen events from one direction and then you start to see them from the other. This Reverse-Flash is not exactly the Reverse-Flash that we saw disintegrate at the end of the year. It's a Reverse-Flash from an earlier timeline. It's not the Earth-Two Reverse-Flash, it's the Reverse-Flash. That is, hands down, one of our best episodes."
The episode Kreisenberg refers to is aptly named "The Reverse-Flash Returns." It will air a week after the series returns on January 19. Before that drama unfolds, premiere episode "Potential Energy" features a new metahuman who can slow time. This skill might just come in handy when Zoom shows up to kidnap Patty (Shantel VanSanten), likely at the moment Barry's deciding whether or not to tell her he's The Flash.
Barry and his team will face a lot of danger and emotional drama in the coming weeks, while viewers will have to struggle to keep track of it all. The mind-bending question many will have is how, if Eobard Thawne was wiped from the reality our heroes have been living, how can he appear from an earlier time? We'll have to assume all these timelines are still floating out there somewhere, and since Eobard existed before Eddie wiped him out in our current timeline, he could still be locked in one of those earlier realities. Though as Captain Janeway (Kate Mulgrew) of Star Trek: Voyager once said, "The past is the future, the future is the past...it all gives me a headache."
The Flash airs Tuesdays @8pm on The CW. Arrow airs Wednesdays @8pm on The CW. DC’s Legends of Tomorrow premieres on The CW on Thursday, January 21, 2016.