Throughout the series, Barry’s character has generally been one of optimism and focused on doing the right thing. This includes never killing, even if it appears to be his only option. He’s often compared to Oliver Queen, who kills frequently and praised for having strong morals. So it comes as a surprise to see him give in to temptation when Dr. Russo offers him an enticing way to live.
Using Ralph as a decoy, Dr. Russo infects and nearly kills him. With the help of Caitlin’s ingenuity and a blood transfusion from Barry, Ralph manages to pull through. However, the transfusion allows Dr. Russo to infect Barry, and invade his body. The infection doesn’t hit him until he makes it home and collapses into a fever dream. In what is described as a prison similar to his time in the Speedforce, Barry faces his greatest fears and desires. He wants nothing more than to have a family with Iris and raise Nora– he doesn’t want to be the Flash and die in the upcoming Crisis. Dr. Russo explains, by joining him, Barry will be strong enough to live through the Crisis. Barry will not only have his family but the ability to save the unsavable.
Trying to save Barry from giving in is the Speedforce itself. Taking the form of his mom, it guides him with the wisdom of the universe. It tries to enforce the belief that it’s the universe’s future that matters more than Barry’s need for a family– not a compelling argument for someone so desperate. In the real world, Barry is found by Caitlin and Cisco, who try to help him battle the infection while he struggles to make a choice. Together they manage to help Barry pull through, and we assume he rejected Dr. Russo’s offer. When Barry wakes up, everything looks to have worked out. He’s focused on the Crisis and doesn’t seem to have any lasting effects. It isn’t until Iris visits and lets Caitlin and Cisco know that this isn’t her Barry, and something has gone wrong.
Just like the other zombies, Dr. Russo has turned, Barry is under his control. He breaks out of Star Labs, with no indication if he can be saved. Thus far, no one has been able to be rescued from Dr. Russo’s infection; they’ve tried a couple of cures and nothing has taken.
With the Crisis just a day away, Barry is gone, Ralph is down for the count and Frost effectively scared silent, I’m not sure how team Flash will be able to help during the Crisis. Nash is still on his hunt for the Monitor, but there has been little progress in that search.