Here's the schedule for Elseworlds, this year's Arrowverse crossover, and how you can watch all three episodes. The CW's annual crossover is the biggest event on their superhero universe's calendar - but Elseworlds is no ordinary crossover. It also introduces Batwoman (Ruby Rose), the Arrowverse's newest superhero, and will open the door to a Batwoman solo series set in Gotham City.

Each crossover has grown in scale as the Arrowverse has evolved; 2016's Invasion! and 2017's Crisis on Earth-X spanned all four Arrowverse series where they fought aliens and other-dimensional Nazis, respectively. For 2018's Elseworlds, the crossover is slightly scaled back, at least in the number of series participating. Elseworlds will span The Flash, Arrow, and Supergirl only; DC's Legends of Tomorrow will be sitting this event out.

Related: Why Legends of Tomorrow Aren't In The Elseworlds Crossover

However, that doesn't mean Elseworlds will be any less epic. The superheroes will assemble to battle a threat to multiple Earths by the villainous Arkham Asylum doctor John Deegan (Jeremy Davies) and a powerful being called the Monitor (LaMonica Garrett). This will not only require Green Arrow (Stephen Amell), The Flash (Grant Gustin), and Supergirl (Melissa Benoist) to join forces, but will also guest star Superman (Tyler Hoechlin), introduce Lois Lane (Elizabeth Tulloch), an evil Black Suit Superman, and John Wesley Shipp reprising his role as the Flash from his 1990 CBS series. Plus there are expected to be other Easter eggs and surprises for DC fans.

Just as Barry Allen and Oliver Queen are switching bodies in Elseworlds, with Amell playing the Flash and Gustin playing Green Arrow, two of the series are also switching timeslots. The Flash is kicking off the event by temporarily moving into Supergirl's Sunday night timeslot and Supergirl moves to The Flash's Tuesday night berth to close out the crossover. With that in mind, here's the complete Elseworlds' schedule and The CW's synopses:

Sunday, Dec. 9th @8pm: The Flash Season 5, Episode 9: Elseworlds, Part 1

This episode will mark the second time Barry Allen has traveled to Supergirl's Earth-38, but it will be a first for Oliver Queen. Meeting Superman and Lois Lane will also be a first for both Green Arrow and The Flash. A cool Easter egg to look out for: the Kent Farm is the same one from Smallville.

When Barry Allen (Grant Gustin) and Oliver Queen (guest star 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 (guest star Melissa Benoist) help and travel to Smallville on Earth-38 where they end up meeting Kara’s cousin, Clark Kent (guest star Tyler Hoechlin), and intrepid reporter, Lois Lane (guest star Elizabeth Tulloch).  LaMonica Garrett guest stars as The Monitor.

Monday, Dec. 10th @8pm: Arrow Season 7, Episode 9: Elseworlds, Part 2

This is the episode that introduces Batwoman and Gotham City. It should also answer some burning questions fans have about where Batman is in the Arrowverse.

With Oliver (Stephen Amell) and Barry (guest star Grant Gustin) still stuck in the other’s bodies, the two get a lead on John Deegan (guest star Jeremy Davies) and head to Gotham City with Supergirl (guest star Melissa Benoist) to figure out why their reality has changed.  While there, they meet the mysterious Kate Kane (guest star Ruby Rose) who provides them with information that leads the group to Arkham Asylum.

Tuesday, Dec. 11th @8pm: Supergirl Season 4, Episode 9: Elseworlds, Part 3

Arrowverse Elseworlds Supergirl Flash Arrow

Supergirl closes out Elseworlds and is expected to feature a battle against the evil Black Suit Superman. The final chapter could also contain some huge surprises that will affect the Arrowverse going forward.

Supergirl (Melissa Benoist), The Flash (guest star Grant Gustin), Green Arrow (guest star Stephen Amell) and Superman (guest star Tyler Hoechlin) engage in the battle of their lives.

Next: Elseworlds Trailer Breakdown: 10 Secrets And Reveals About The Arrowverse Crossover