John Diggle arrives in Central City with a weapon to help Barry stop the Godspeed War. Meanwhile, Allegra and Ultraviolet's new bond is put to the ultimate test, while Joe and Kristin Kramer are hunted by a former colleague of hers.

The Flash enlists a host of speedster allies, including Iris and his children from the future—Bart and Nora West-Allen—to end the speedster war and defeat a deadly new adversary: the villainous Godspeed.