White Canary, Supergirl and Batwoman raise a glass to Green Arrow who sacrificed himself for millions of people from Earth-38 and determine to stop the same fate falling upon other earths. Harbinger and the Monitor arrive requesting access to the Atom’s lab. Harbinger travels to Earth-74 and a run down Waverider ship where the AI is named Leonard – the same voice of Leonard Snart aka Captain Cold from Earth-1. Heat Wave appears and takes little persuading to team up with Harbinger and let her use his Waverider.
Returning to Earth-1, the Monitor reveals the existence of seven “beings of the purest will” known as Paragons who can defeat the Anti-Monitor. He has learned of these people from the Book of Destiny which he has recreated from a previous time and stored within the Waverider’s library.
His new plan is to find these Paragons – he already has the Paragon of Hope in Supergirl, and White Canary is the Paragon of Destiny. The Paragon of Truth is another Kryptonian who has lost everything – Superman and Lois elect to find him. The Paragon of Courage is known as “the Bat of the Future” and is on Earth-99 where Bruce Wayne has dedicated his life to his mission.
As Supergirl mourns the loss of her world, she’s surprised by the Monitor bringing Lex Luthor on to the ship. Batwoman attempts to cheer Supergirl up by persuading her to go with her to Earth-99 and find the Batman of the future.
Harbinger is unable to stop Luthor stealing the Book of Destiny, but the Monitor is unconcerned.
Flash and Iris discuss the possibility of using another Earth’s Lazarus Pit to bring Green Arrow back to life, and she tells him that the Monitor asked her to find the helpless Kryptonian. White Canary and Mia also discuss using the Pit to bring Green Arrow back, with Canary trying to dissuade her.
On Earth-99, Batwoman and Supergirl appear at a derelict Wayne Manor and break in to be confronted by Luke Fox and an aged, exoskeleton wearing Bruce Wayne. Luke takes Supergirl to the library while Bruce and Batwoman talk, with him revealing that Earth’s Kate had died.
On Earth-75, Lois and Superman receive a message from Iris telling them Luthor is not only alive but travelling through the Multiverse killing Superman. They see a news broadcast showing they’re too late – Luthor has just killed the Superman of Earth-75.
Back on the Waverider, Flash and Mia ask John Constantine to help them with their Lazarus Pit problem and he is able to find an Earth with a workable Pit.
On Earth-167, Superman, Lois and Iris find Clark Kent in Smallville and try to warn him that Luthor is about to kill him. Before they can say more, they are ejected from the Earth by Luthor who appears with the Book of Destiny. Luthor admits he wishes to kill every version of Superman in existence and removes a piece of Kryptonite to threaten him with. It has no effect on Clark, who simply tosses it away and reveals that he gave up his powers. Luthor cannot believe he would do that and leaves him and his Lois to their fate.
On Earth-99, Batman rejects being called a Paragon of Courage and tells Batwoman that he has killed multiple enemies and that his Kate became Batwoman and was killed. Batwoman tries to convince him, however, that he’s needed.
The Atom works on a Paragon detector while Heat Wave babysits Jonathan, Lois and Clark’s son.
On Earth-96, Superman, Clark, and Lois head to the Daily Planet where they bump into that Earth’s Clark (who happens to look a lot like the Atom).
On Earth-99, Supergirl sees a collection of trophies the Batman has collected, including a cracked pair of glasses that belonged to Superman. Luke acknowledges that Batman killed Superman on this Earth, the battle being the reason for Bruce’s exoskeleton.
Back on Earth-96, the heroes warn that Earth’s Superman that Luthor is different and Superman-96 tells them of having lost his friends and wife to an attack from “a reject from Gotham” – showing himself to be the Paragon of Truth. The two Supermen agree to face Luthor first before returning to the Waverider. Luthor arrives with the Book and makes Superman-96 want to kill Superman-1.
The two Supermen take to the skies and battle each other above Metropolis before Superman-96 attempts to kill Lois. Before that happens, Lois knocks out Luthor and Lois and Iris use the Book of Destiny, combined with Lois talking him down, to rid him of Luthor’s control.
Constantine, White Canary, Flash and Mia head to Earth-18 and find a Lazarus Pit. As they prepare it, they are joined by Jonah Hex who tries to stop them. Eventually Green Arrow is lowered into the Pit.
On Earth-99, Bruce rejects Batwoman, and Supergirl tells her Bruce killed Superman. With the Kryptonite embedded in his exoskeleton, Bruce attacks Supergirl.
On Earth-18, a crazed and deranged Green Arrow emerges from the Pit and attacks the others.
Batwoman fights Bruce, preventing him killing Supergirl, but accidentally causes his exoskeleton to short out, killing him. With his dying breath he tells her there is no hope.
Back on the Waverider, Superman-96 meets the Atom, while Lex Luthor is imprisoned in the brig. They’re joined by the Monitor, then Supergirl and Batwoman. Supergirl calls out the Monitor for using Luthor to direct the others to Superman-96 which resulted in Luthor killing numerous heroes. The Atom fires up his Paragon detector and it reveals that Batwoman was the Paragon of Courage all along.
On Earth-18, Constantine tries to bring the soul of Green Arrow back to inhabit the resurrected body but is having a problem.
On the Waverider, Supergirl and Batwoman talk and Supergirl convinces Batwoman that she will be her own person, and Supergirl considers using the Book of Destiny to restore her world. After she has gone, Batwoman reveals she took the Kryptonite from Bruce’s exoskeleton.
Harbinger vanishes from the Waverider and appears in STAR Labs and is confronted by the Anti-Monitor.
 – Earth-74 home to the retired Legends of Tomorrow where Heat Wave is living in the Waverider.
 – Earth-99 is the home of an aged Bruce Wayne, played by Kevin Conroy who provided the voice of Bruce Wayne in Batman: The Animated Series which debuted in 1999, thus giving the Earth it’s number.
 – the exoskeleton Bruce wears is the same as that worn by the elderly Bruce Wayne in the KINGDOM COME comic book series.
 – Earth-75 is named for SUPERMAN #75 which featured the Death of Superman in the mid 90’s.
 – the image on the screen references art used in the Death of Superman storyline and which was used as the cover for the collected edition.
 – Earth-167 is home to the characters of Smallville, the series that ran between 2001 and 2011 and which featured the exploits of Clark Kent before he officially became Superman. It’s named after the birth year (1967) of Alfred Gough one of the creators of the series.
 – Earth-96 is named for the KINGDOM COME series first published in 1996 and from which several visuals are taken in this episode.
 – Superman-96 wears the same costume as the character does in KINGDOM COME; played by Brandon Routh (who plays the Atom in Legends of Tomorrow) this is also the Superman from the Christopher Reeves movies who was played by Routh in Superman Returns.
 – the “reject from Gotham” is the Joker who gassed and killed many of Superman’s colleagues (including Lois Lane) in KINGDOM COME. The art shown on the wall is from that series.
 – Earth-18 may be named for Jonah Hex whose adventures took place in the 1800’s.