Supergirl Season 4 Finale: 9 Ups & 2 Downs From 'The Quest For Peace'

2. Crisis On Unexpected Earths

The finale's closing moments saw the unexpected return of The Monitor (who also turned up in last week's Arrow finale) and, in the space of a few seconds, he managed to turn everything we knew on its head, as he freed the Martian known as Malefic a.k.a. J'onn J'onzz's twin brother and arch-nemesis.

If that wasn't enough, he informed the vengeful Martian that he had one more place to visit and, in the blink of an eye, stood over Lex Luthor's dead body, before smirking and waving his hand in a rather, well, Monitor-like fashion.

As the Elseworlds crossover teased, The Monitor is undoubtedly going to have a major role to play in the upcoming Crisis On Infinite Earths, so having him and/or the Crisis itself factor into the cliffhangers in the finales of Arrow, The Flash and now Supergirl was a genius idea on the part of the Arrowverse's creative team as it has, without a doubt, increased anticipation for the major TV event. The only question is: Whose side is he actually on?

In the words of Eobard Thawne, "See you at our next Crisis" Monitor.