Here is a in-depth, but easy to follow review of what is happening in the Crisis On Infinite Earths cross-over event on the CW.
Clark and Lois are among the first to experience loss in the crisis as the red sky engulfs Argo City where they moved to live with there son, Jonathan. They end up shipping him via pod to earth. Similar to how Clark was saved by his parents on Krypton.
Lyla is the Harbinger and gathers the heroes to Earth-38 to plan for the crisis and save the multi-verse. There is a quantum tower in National City and the heroes are going to use it as a stronghold. The heroes also have to save baby Jonathon because in all the commotion, he was sent to Earth -16 2046. The group successfully recovers baby Jonathan and begins to prepare a line of defense and lifeline for evacuation.
Barry tells Oliver that he’ll disappear because of the crisis while Oliver dies. Oliver calls to the Monitor because in last year’s cross over event, Oliver made a deal that Barry and Cara would be unharmed, but The Monitor says the deal Oliver made was for the last big event and now this is a different situation.
The world begins to get engulfed while the heroes try to evacuate the planet, Oliver gets mortally wounded despite having The Flash, Superman and Super Girl with him. The Monitor admits Oliver should still be alive, however, he sacrificed himself to help save lives.
Nash Wells (also known as the Pariah) arrives to tells the group he let the Anti-monitor out. Remember, in the previous episode of The Flash, he was sucked into the vault with the suspect-voice telling him to pledge. Now he has to watch as worlds get destroyed. During this scene the heroes watch Arrow die.
The heroes regroup on a version of the Wave Rider that Lyla commandeered along with Heatwave. The Wave Rider will be an important base for the heroes. The Monitor tells the heroes that seven of them are needed for this next phase according to the Book of Destiny.
The Book of Destiny describes seven paragons, Super Girl (Paragon of Hope) and Sarah Lance (Paragon of Destiny) are already known. They have to find a Batman from the future to be the Paragon of Courage and a Kryptonian (Superman) to be the Paragon of Truth.
Barry and Iris share a moment and hope that the Monitor is wrong about Barry’s fate because he was incorrect about Oliver. Barry also expresses that he wants to use the Lazarus Pit to bring Oliver back. Oliver’s daughter, Mia, also wants to bring him back so she takes Sarah, Barry, and Constantine with her to Earth-18 where they find the Lazarus Pit and revive Oliver. But, Constantine couldn’t grab Oliver’s soul, so he is an empty vessel now.
Lex Luther is around and steals the Wave Rider along with the Book of Destiny to kill every version of Superman. Meanwhile, Lois and Clark are looking for Superman as well to be the Paragon. On Earth-167 we catch up with Smallville Clark Kent. Iris, Lois, and Clark tell him about Lex’s plan. Lex arrives and teleports them away. He tries to hurt Clark (Earth-167) by using Kryptonite, but it doesn’t work because he no longer has powers, so Lex leaves.
Batwoman goes to find Batman with Super Girl. We find out he’s a bit darker than we’re used to because he does not have the rule against killing villains. He reveals he killed Superman, which doesn’t sit well with Cara. Bruce ends up dying via electrocution and his last words to Kate are that there is no hope.
Still searching for Superman (truth), Iris, Lois, and Clark go to Earth-96. We meet Superman of Superman Returns. We find out that the Joker attacked and Lois ended up dying as well as some others. Somehow Lex sabotages things and Superman(96) fights Superman (38). Luckily, Iris and Lois retrieved the Book of Destiny from Lex and help bring Superman (96) back to their side.
When the group comes back together on the Wave Rider, we find out Batwoman is the Paragon of Courage because of how she handled the tormented version of Batman. Cara tells Kate that she will restore Earth-38 (her earth that was destroyed in the last episode) using the Book of Destiny. Kate is skeptical of that dangerous idea. As a side note, Batwoman has kryptonite now.
To end the episode, we see the Anti-Monitor summon the harbinger.