Ep 21. Cause and Effect

After last week's dramatic events, "The Flash" returns to form with a solid episode that gives us everything we've come to expect from the series. In "Cause and Effect," we see Barry Allen's attempt to stop Savitar from killing Iris West spin wildly out of control, resulting in yet another villainous doppelgänger and some fun, if not particularly deep exploration of time travel.

As the episode begins, we find Barry attempting to work through the moral implications of defeating Savitar before he can kill Iris. Much to his dismay, he soon realizes there's only one way to do it: he must go back in time and capture Savitar before he ever becomes the monster we know and hate. Of course, as fans of the show know, messing with the timeline is rarely a good idea.

The first thing to go wrong is the simple matter of getting everyone on board with the plan. Cisco is hesitant to help, and even HR (who is quickly proving himself to be valuable addition to the team) is more than a little skeptical. Once they do eventually convince everyone, they discover that getting Barry up to speed (ha!) on where and when he needs to go is a bit more complicated than they'd hoped. Cue some classic Dr. Wells' techno babble and an incredibly nerdy whiteboard diagram that serves to move the story forward in a satisfying, if not exactly thrilling way.

After a quick trip to the future where they discover things have gone horribly wrong (it's "The Flash," what else did you expect?), they settle on a plan that involves Barry moving fast enough to generate a wormhole that they can all use to travel back in time. As these things go, it seems pretty straightforward. Naturally, once they travel back to the day before Iris is due to die, things start going off the rails.

I won't spoil the specifics, but suffice it to say that Barry realizes even his best-laid plans can't account for every variable. As a result, he has to resort to a desperate, last-minute Hail Mary that ends up creating another villain for him to fight in the form of the "God of Speed." I'm not sure it was strictly necessary to have yet another version of The Flash's evil, super-fast doppelgänger, but it provides some great action and a chance for Barry to shine in true superhero fashion.

All in all, "Cause and Effect" is a satisfying episode that doesn't necessarily move the overarching Savitar storyline forward in any significant way, but it does provide a fun, action-packed romp through the familiar territory of time travel and warring timelines. If you're looking for another great installment of "The Flash," look no further.