The Flash 3x21 "Cause and Effect" Promo & Synopsis
Watch the preview for next week's episode of The Flash, "Cause and Effect."
Barry (Grant Gustin) takes drastic measures to stop Savitar. Meanwhile, H.R. (Tom Cavanagh) continues to push Tracy Brand (guest star Anne Dudek) to design the trap for Savitar and Killer Frost (Danielle Panabaker) returns with an interesting proposal. David McWhirter directed the episode written by Judalina Neira & Lauren Certo (FLA321). Original airdate 5/9/2017.
The Flash airs Tuesdays at 8pm ET on The CW starring Grant Gustin.
Updated: with extended trailer: