Crossover.
Kate Kane (Ruby Rose).
You shape the world as you see fit. — the Monitor.
The Flash, Arrow, Supergirl Crossover.
The Monitor’s mission is to seek out the right heroes by putting them through the ultimate test. If they fail, he wipes out that Earth and moves on to the next.
Part 1 – The Flash.
When Barry Allen (Grant Gustin) and Oliver Queen (Stephen Amell) 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 (Melissa Benoist) help and travel to Smallville on Earth-38 where they end up meeting Kara’s cousin, Clark Kent (Tyler Hoechlin), and intrepid reporter, Lois Lane (Elizabeth Tulloch).
Part 2 – Arrow.
With Oliver Queen (Stephen Amell) and Barry Allen ( Grant Gustin) still stuck in the other’s bodies, the two get a lead on John Deegan (Jeremy Davies) and head to Gotham City with Supergirl ( Melissa Benoist) to figure out why their reality has changed. While there, they meet the mysterious Kate Kane (Ruby Rose) who provides them with information that leads the group to Arkham Asylum.
Part 3 – Supergirl.
Supergirl (Melissa Benoist), The Flash (Grant Gustin), Green Arrow ( Stephen Amell) and Superman ( Tyler Hoechlin) engage in the battle of their lives.
The annual DC crossover on The CW is flipping the order: it starts with The Flash on Sunday, December 9th, followed by Arrow on Monday, December 10th and ends with Supergirl on Tuesday, December 11th — all at 8 p.m.