Catching Up: The Flash Episode 604, "There Will Be Blood"

In tonight's Halloween episode, the title is "There Will Be Blood" and there's a bio-restorative formula at play. What an opportunity to get an cameo from Swamp Thing that we... don't get. But, moving onward.

Flash (GRANT GUSTIN) is still resigned to the fact that he is fated to die in the upcoming Crisis in order for the universe to survive. In the previous episode, Flash tried to prepare the team for his inevitable passing by taking Killer Frost (DANIELLE PANABAKER) under his wing to teach her to be a better hero. This week, he decides to spend some one-on-one time with Cisco Ramon (CARLOS VALDES), the former Vibe, because he's picked him to be the team leader when he's gone. Which, I suppose, will be Team Frozen Stretch, without the speedster around.

But Cisco isn't giving up on saving Flash, despite Flash's urging that he instead focus on saving Dr. Ramsey Rosso (SENDHIL RAMAMURTHY) instead. That's when the latest Harry Wells (TOM CAVANAGH) drops in with a plan to do just that--offering to help them steal a biorestorative formula from a company that itself stole it from someone who somehow got it from a Dominator moon (harkening all the way back to the first CW crossover event). In return for his help, he wants them to build... some Arrowverse-scifi-gizmo. And when Flash is gone, Cisco learns that the formula--which could ostensibly restore Rosso's destroyed blood cells--could also protect a person from contact with anti-matter.

Sidelong to this, Iris (CANDICE PATTON) approaches Ralph (HARTLEY SAWYER) with some new information for the Sue Dearbon missing person case he is working, to find that Ralph has given up. He's despondent over Barry's upcoming death, and is taking a nihilistic approach to things now.

Meanwhile, Ramsey Rosso tests the biorestorative formula given him by Barry and Cisco, but his condition is too far gone for it to work. He's back to having to intake blood infected with dark matter--blood he can project and control. But it's not enough until he figures out why his first victim's blood worked--because the victim was afraid, overloading his blood with epinephrine. Rather than take donated blood and shoot himself with an epi-pen, he instead opts for terrifying humans before killing them and taking in their blood. Oh, and bonus side effect: anyone he kills he can control, zombifying them!

It's just the kind of villain you'd want for Halloween, even though he (of course) gets away to be a villain for the rest of this season. And as for the upcoming Crisis, the Eternium, and the...thingamajiggie that Wells needed, we find out that this Wells is hunting for more than Eternium. He's hunting for Mar Novu -- the Monitor -- and the device helps to track him down.

Interesting theory currently going around: Wells found Eternium in the previous episode -- and found a faint trace of it from Iris. Could it be that there's something about Iris previously unrevealed? In the comics, Iris was a transplant from the future. Could our Iris, unbeknownst to herself, be from another time?