Part 1 (Supergirl) – December 8, 2019
The Monitor sends Harbinger AKA Lyla Michaels (So at this point she has fully taken on the mantle?) to gather up all the greatest heroes (which includes Supergirl, The Flash, Green Arrow, Batwoman, White Canary, The Atom and Superman) in preparation for the impending Crisis. With all worlds at stake, the heroes suit up for battle while J’onn J’onzz and Alex Danvers recruit Lena Luthor to help them find a way to save the people of Earth-38.
Part 2 (Batwoman) – December 9, 2019
The heroes use Ray Palmer’s invention to track new recruits to help them to save the universe. The Monitor sends Iris West-Allen, Clark Kent and Lois Lane in search of a mysterious Kryptonian (Brandon Routh or Tom Welling? I think Tom Welling but along the way they find Brandon Routh’s Superman). While Kate Kane and Kara Danvers head out to find Bruce Wayne (Earth-1’s Bruce Wayne? Clearly he did not want to be found and considering his advanced age I doubt they are going to be using him for anything other than his mind)
Part 3 (The Flash) – December 10, 2019
Pariah (played by Tom Cavanagh and may actually be Nash Wells who I wonder if he will still be Pariah after the crossover AKA will he be a part of the rest of the season of The Flash) travels to whatever Earth Black Lightning’s on to get him to help them stop the Anti-Monitor (Jefferson Pierce being an overprotective father and maybe not enough money in the crossover budget obviously decides to leave his daughters out the fight). This happens after Flash-90 AKA Barry Allen (played by John Wesley Shipp) shares what he learned from his battle in Elseworlds, a battle of which he was one of the only remaining survivors. With the help from Black Lightning, Barry Allen, Cisco Ramon (no Vibe yet?) and Killer Frost come up with a plan that could save them all. Meanwhile, Iris has a heart-to-heart with Ryan Choi (the guy who is supposed to become the new The Atom), while Oliver Queen and John Diggle return to an old, familiar stomping ground (Nanda Parbat? Russia? Hong Kong? They’ve been everywhere and not just this season).