WARNING: If you don't want to know what happened in this episode, don't read this photo recap!
As per usual, the team has been following one of Roberta's hunches as to where they go next. And now they've found themselves back at a massive factory they've already destroyed. Bad things went down here with Dr. Teller's family, and the team is going back in.
Meanwhile, Roberta Warren is following her hunches deep into the factory. She knows that whatever is here, it's leading to whatever this Black Rainbow plan is. She's desperate for answers, and her dreams are still leading her.
The team searches desperately and relive the fact that a while back, this lab was where they learned where zombies could feel but not fully express themselves. Dr. Teller's zombie wife, in particular, was asking about their son.
Meanwhile, up at the Northern Lights station, Kaya and Citizen Z are looking for any information they can find on Black Rainbow. They're desperate to tell Roberta and the gang that it's a "fourth strike weapon.".
The team gets the radio working but it keeps cutting out. They finally make the most difficult choice and divert the power from Andrew's life support to the radio so they can speak with Kaya and Citizen Z. When Sarge can't do it, Roberta gives him mercy.
Citizen Z and Roberta and both teams put it all together. What they're up against is a fourth strike weapon. Meaning, after the apocalypse, there's another wave coming: to wipe out everything else. Black Rainbow is the "reset" that Zona was working on.