U prvome dijelu spajanja serija Flash i Arrow, Barry je oduševljen kada mu Oliver, Felicity i Diggle pomognu zaustaviti metačovjeka.

Vandal Savage namjerio se na Kendru Saunders pa je Barry mora skriti u Star City s Oliverom u prvom dijelu nevjerojatnog spajanja dviju serija.

King Shark bježi iz zatvora A.R.G.U.S.-a pa Lyla i Diggle putuju u Central City kako bi upozorili Flasha. King Shark pojavljuje se u kući Westovih i napada Joea, Iris, Wallyja i Barryja.

Dominatori vanzemaljski neprijatelji žele izvršiti invaziju ali Flash i ekipa im kvare planove.

When DeVoe assaults an A.R.G.U.S. facility to complete his Enlightenment Machine, Barry realizes the only way he can stop him is if he allows Cisco and Caitlin to accompany him into the facility. Still shaken by Ralph’s death, Barry isn’t sure he wants to risk any more of his friends’ lives and considers taking on DeVoe solo.

When Barry Allen and Oliver Queen wake up one morning and realize they have swapped bodies with each other, the two set off to find out what disturbed the timeline to cause such a shift. However, things quickly go from bad to worse when they present their case to Team Flash and the gang doesn’t believe them. Barry and Oliver realize they need Supergirl’s help and travel to Smallville on Earth-38 where they end up meeting Kara’s cousin, Clark Kent, and intrepid reporter, Lois Lane.

The crossover continues on Arrow S07E09 Elseworlds (II) and Supergirl S04E09 Elseworlds (III).

Pariah enlists Black Lightning to help stop the Anti-Monitor after Flash-90 shares what he learned from his battle in ‘Elseworlds.’ With the help of Black Lightning, Barry, Cisco and Killer Frost come up with a plan that could save them all. Meanwhile, Iris has a heart-to-heart with Ryan Choi, while Oliver and Diggle return to an old familiar stomping ground.

The crossover starts on Supergirl S05E09 and Batwoman S01E09. It continues on Arrow S08E08 and Legends of Tomorrow S05E01.

After "The Citizen" prints an explosive story, Iris' life is threatened; refusing to hide from her attackers, Iris sets out to expose a dangerous organization; Barry must face the consequences of the Crisis and fulfill Oliver Queen's wish for him.

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 Kristen Kramer are hunted by a former colleague of hers.

With a new speedster in town, The Flash gets much more than he bargained for, meanwhile Cecile's powers experience a growth spurt allowing her to aid Team Flash on an entirely different level.

Team Flash throws a surprise birthday party for Barry, but things go terribly awry when Ramsey Rosso crashes the festivities.