SEASON PREMIERE – When an experiment to save Barry’s (Grant Gustin) speed backfires, Nash Wells (Tom Cavanagh) searches for a way to save The Flash and comes up with a dangerous plan. Meanwhile, Iris (Candice Patton) makes a startling realization inside the Mirrorverse and Cecile (Danielle Nicolet) faces off with Rosa Dillon (guest star Ashley Rickards). Alexandra La Roche directed the episode written by Sam Chalsen & Lauren Certo (#701). Original airdate 3/2/2021.