After discovering that Nora is working with Thawne, Barry and Iris disagree about how to handle their daughter in the wake of this shocking news. Team Flash isn't sure they can trust Nora, so they go through her journal to find out exactly how she came to work alongside their greatest nemesis.

When Icicle returns to enact the next phase of his devious plan, Caitlin and her mother, Dr. Carla Tannhauser, must resolve their long-combative relationship to defeat the icy monster. After Barry makes a big decision about their family without consulting her, Iris decides to take matters into her own hands.

Team Flash is on high alert after Cicada II threatens to unleash a dangerous virus that would put all meta-humans at risk.

Barry faces off with his oldest, and most formidable nemesis, Reverse Flash.