Part Five — [s5e1] Crisis On Infinite Earths:

is the concluding chapter of the five-part Arrowverse crossover event, airing as the season 5 premiere of DC's Legends of Tomorrow . Episode Summary

The episode follows the heroes as they wake up in a called Earth-Prime , where several previous realities—including those of The Flash , Supergirl , and Black Lightning —have merged into one. Crisis On Infinite Earths - IMDb [S5E1] Crisis on Infinite Earths: Part Five