The biggest mystery plaguing the first season of The CW's excellent "The Flash" is the identity of Barry Allen's (Grant Gustin) arch-enemy, the Reverse Flash.

We'll take a pause for those of you not steeped in comic book lore to stifle their laughter (seriously, we won't get into his other silly name, Professor Zoom), because the villain is actually terrifying. In the show alone, he's probably responsible for the death of Barry's mother, he's threatened the nicest police officer in history, Joe West (Jesse L. Martin), and according to an interview with EW, he's about to make Team Flash face their biggest foe yet.

But one thing the interview does not reveal, and something that won't even be revealed during the episode airing December 9, "The Man In The Yellow Suit," is who the Reverse Flash really is. With that in mind, here are the likely suspects:

5. Eddie Thawne

Though nothing has indicated Eddie Thawne (Rick Cosnett), the affable boyfriend of Iris West (Candace Patton) and partner of Joe West is anything but a nice guy, comic book readers know a little better. Eobard Thawne is the name of the original Reverse Flash from the books, which is pretty close to Eddie. Could this Thawne be secretly an evil, time-traveling genius who murdered his friend's mother? Sure. But it's also possible that Eddie is an ancestor of Eobard, and may take on the villainous mantle at a later date. Hence ranking him last.

4. Henry Allen

This would be a doozy of a twist, as Henry Allen (John Wesley Shipp) has been in prison since Barry was a kid for murdering his wife Nora Allen (Michelle Harrison). Right now, the suspicion is firmly off Henry, but given Shipp has already played The Flash once, in the '90s TV show, wouldn't it be great to twist our expectations of the actor to some very dark places? Plus, when time travel is in play, rules of character arcs go out the window.

3. Barry Allen

This is our favorite theory so far, and it takes some crazy clues to back up. But who better to be a Reverse Flash that The Flash himself? Again, once you get into time travel, alternate realities and versions of characters open up as possibilities. We've seen as recently as last night's episode that the energy (not yet called Speed Force, like it is in the comics) coming out of Barry can have a decidedly yellow hue, like the energy that was coursing around Nora the night of her murder.

Barry doesn't seem to have a dark side, but with all the changes his body is going through -- in last night's episode Caitlin Snow (Danielle Panabaker) showed off a look at Barry's mutated cells, which again had taken on a decidedly yellow hue -- what if one of those changes turns him evil? And what if Barry needs to make a choice? It would be a pretty potent metaphor to see the younger Barry fighting his older, evil self for the life of his family.

And certainly, our next suspect has been very interested in the course of Barry's future. So despite what we're about to say about that suspect, what if he's interested in making sure Barry heads to the path of good, rather than evil?

2. Harrison Wells

Let's talk about Harrison Wells (Tom Cavanagh). Despite every other theory we've put out there, nearly every piece of evidence is pointing to Harrison Wells as the Reverse Flash. He's clearly deeply secretive, is - most likely - a time traveler, and very interested in manipulating Barry's future. Not only that, but as he showed last night (November 25), he's willing to sacrifice anything, and anyone to make that future happen.

Add in the post-credits tag where he took a genetic sample from the guest star villain in order to find out how the guy stole the Flash's powers, and you've got a prime set-up for Wells little experiment going very, very wrong.

That's not the only evidence, either. Geoff Johns - executive producer of the show - rebuilt Reverse Flash for his run on the comics as a villain bent on making Barry into a better hero. And he did it in the most horrible way possible: by time traveling and threatening Barry's family, to teach him a lesson about tragedy. That certainly links up with something the increasingly unhinged Wells would do.

But wait, there's more! Elements of a "Flash" movie script that was written years ago by show producer Greg Berlanti have leaked their way into the show. One that may or may not play out? Eobard Thawne traveled back in time to an alternate dimension where he built the particle accelerator that gave The Flash his powers, and then trained him... just so he could defeat him later.

This arc is very close to the current arc being played out by Wells, with some changes. So could it end up the same way? We'd believe it, too, if it wasn't for our last suspect.

1. This Guy

Seriously, what is this guy's deal? You just can NOT trust him.

Who do you think The Reverse Flash is? Let us know in the comments below!