John Diggle arrives in Central City with a weapon to help Barry stop the Godspeed War; Allegra and Ultraviolet's new bond is put to the ultimate test; Joe and Kristin Kramer are hunted by a former colleague of hers.
When Ultraviolet returns to Central City, Allegra is determined to find her cousin and change her heart; Joe finds evidence that Kristen Kramer may not be the good cop she appears to be.