Ryn discovers a refuge of injured mermaids that escaped Tia’s violent takeover. Ben and Xander get caught in a battle with Tia’s troops. Maddie feeds Robb half-truths to secure his…

Felicity and Ray Palmer pay a visit to S.T.A.R. Labs for help getting Ray’s ATOM suit to work, and ask Cisco for help. Meanwhile, a young tech expert raises havoc…