When an experiment to save Barry's speed backfires, Nash Wells searches for a way to save The Flash and comes up with a dangerous plan. Meanwhile, Iris makes a startling realization inside the Mirrorverse and Cecile faces off with Rosa Dillon.

When an army of Godspeeds attack Central City, Barry and Iris must put their family plans on hold and focus on the latest threat to their home. Meanwhile, Chillblaine is released from prison and claims to be reformed but Frost has her doubts.