That said, it's possible that Nora learning what Thawne did to her grandmother will fracture their relationship and put an end to their work together, even if only temporarily. We'll have to wait and see. Unfortunately, we may have a while to wait. The final episode of The Flash before winter hiatus will be the first leg of the gigantic "Elseworlds" crossover, which kicks off with The Flash on Sunday, December 9 at 8 p.m. ET in Supergirl's usual time slot. Be sure to tune in to see Batgirl in the flesh as well as learn if Monitor's introduction is the first step toward a "Crisis On Infinite Earths" arc.