Dr. Wells' former protégé, Hartley Rathaway, returns to seek revenge on his mentor. Meanwhile, Iris is hired as a cub reporter; Cisco recalls his first day on the job at S.T.A.R. Labs; and Joe asks Eddie for a favor but asks him to keep it a secret from Barry.

Caitlin takes Barry out to a local karaoke bar to help them both find new loves. Caitlin strikes out but Barry meets a sports reporter and asks her out for a date. Meanwhile, Cisco considers Hartley's dangerous offer; and the team search for Shawna, a meta-human with teleportation powers who just busted her boyfriend out of Iron Heights.

After the shocking revelation that Zoom is Jay Garrick, Barry is more determined than ever to get back to Earth-2 to stop Zoom forever. Desperate to find a way to increase his speed, Barry decides to travel back in time and masquerade as his earlier self in order to get his arch-nemesis, Dr. Harrison Wells/Eobard Thawne, to teach him how to run faster. However, things don’t go as planned and Barry is stunned to face familiar foe Hartley Rathaway, as well as old friend Eddie Thawne. Iris makes peace with her past in order to embrace her future.

Feeling overwhelmed with all the changes since Crisis, Barry conducts an experiment that goes awry and puts him directly in Gorilla Grodd’s path. Expecting the worst, Barry is surprised when Grodd asks for his help. Unfortunately for both The Flash and Grodd, things get worse when another villain appears – Solovar. Meanwhile, Iris works with Eva to escape the Mirrorverse.

When Godspeed returns, Barry turns to Hartley Rathaway for help. However, things get tense quickly after Barry realizes one of the changes from Crisis is that The Flash and Pied Piper are now enemies. Meanwhile, Iris tries to escape the Mirrorverse.

Barry feels guilty for what happened to Caitlin, and Mark comes up with a plan that makes everyone skeptical. Meanwhile, Red Death looms in Central City and commands that failure is not an option. Joe asks Cecile to make a choice that leads Cecile to think about the greater good. Allegra and Chester take a step in a new direction. Lastly, old friends pay an unexpected visit to S.T.A.R. Labs.

Barry and Iris start to put together the pieces of what's happening in Central City and believe they know what the Rogues are after. Team Flash works together and recruits some unlikely allies to help, and the plan does not go as Team Flash expects. Meanwhile, Allegra does her best to avoid having a conversation with Chester.

The Flash is forced to make an impossible choice. With the power out in the city, Team Flash calls upon the Rogue Squad to help as Iris is visited by an old friend. Joe and Cecile work on finding a balance.

As the Red Death wreaks havoc on Central City, Barry and Iris come up with a plan and turn to Cecile for help. Barry is faced with what he thinks was his greatest mistake and the Red Death's greatest success. Khione wants to help Team Flash, but Barry can't risk losing her. Joe gives Barry a much-needed pep talk.