Dani and Marie agree to help Ro recover trapped Sentinels but on their first attempt, something goes wrong and Ro contracts a dangerous and potentially deadly infection.

With Ro out of commission, it's up to the Norris sisters to figure out how to fix Ro and keep what has happened to her, and their role in it, a secret.

Hey discovers them, making him their most urgent threat until a fully recovered Ro convinces them that her second in command can be trusted.

Still unsure about Hey, Dani and her sister agree to another Sentinel rescue mission. This time they travel to Blue Mountain's caves, where there are reports of dozens of missing Sentinels.

They are followed by someone from Corporate and Ro is faced with the choice between continuing her mission to save dozens of Sentinels and sacrificing one, or giving up.

But Ro forgets that her choice will affect Dani and Marie. Will the sisters decide that Ro and Hey are too big a threat?