- Grant Gustin (Barry Allen / The Flash)
- Candice Patton (Iris West-Allen)
- Danielle Panabaker (Khione)
- Danielle Nicolet (Cecile Horton)
- Kayla Compton (Allegra Garcia)
- Brandon McKnight (Chester P. Runk)
- Jon Cor (Mark Blaine / Chillblaine)
The Flash — S3E21
Episode: Cause and Effect
Air Date: 2017-05-09
Runtime: 42 min
Overview
Barry takes drastic measures to stop Savitar. Meanwhile, H.R. continues to push Tracy Brand to design the trap for Savitar and Killer Frost returns with an interesting proposal.