The CW has shared over twenty promotional images from The Flash episode 19, "Who is Harrison Wells?" - featuring Paul Blackthorne and Katie Cassidy from Arrow.
In this episode, airing April 21., Joe and Cisco head to Starling City to continue their investigation of Dr. Wells. While in town, the duo enlists the help of Captain Lance, and Cisco meets the Black Canary, who asks him for a favor. To learn what is meanwhile happening in Central City, check out the episode guide where you can read the full episode description!