Season 1, Episode 16 -"Rogue Time" - The Flash learns that Captain Cold and Heat Wave have returned to Central City, and that Snart has brought along his sister Lisa to help wreak havoc on the town.
Season 1, Episode 19 -"Who Is Harrison Wells?" - Joe and Cisco head to Starling City to continue their investigation of Dr. Wells. While in town, Cisco meets the Black Canary, who asks him for a favor. Meanwhile, Barry races to catch a meta-human who can transform himself into any person he touches, including the Flash.
Season 2,Episode 5 -"The Darkness and the Light" - Barry learns a new breacher, Dr. Light, has come through the portal and sets off to capture her. Jay tells Barry that Dr. Light was not a threat on Earth-2 and that Barry can reason with her. However, during a fight with The Flash, she blinds him and drops some shocking news about Zoom. Meanwhile, Barry and Patty go out on a date.
Season 2,Episode 11 -“The Reverse-Flash Returns” – Cisco gets a vibe of Eobard Thawne, but 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.