Barry enjoys the annual tradition of tree trimming and gift exchange with Joe and Iris. He gives Iris a touching gift, but the moment is interrupted by Eddie’s arrival.

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 with her insect drones, and Barry asks Ray for help dealing with her.

Barry and the team look for another Firestorm match for Dr. Stein. When the team meets Jefferson "Jax" Jackson, Caitlin has her reservations about whether Jax is the right match for Dr. Stein. Iris surprises Joe while Barry and Patty grow closer.

When Cisco gets a vibe of Eobard Thawne, Barry and the team don’t believe it. But, after an attack at Mercury Labs, Christina McGee confirms that the Reverse Flash is back. Meanwhile, Iris and Francine share a nice moment that brings Iris closer to her brother, Wally.

After Zoom unleashes an army of Earth-2 meta-humans on Central City, Barry is shaken when he sees their leader is the Black Canary’s Earth-2 doppelganger, the Black Siren. Meanwhile, Wally takes to the streets to help The Flash stop the meta-humans, which worries Joe. Iris and Henry are concerned about Barry taking on Zoom.