After learning the Dominators’ plan for the world, the Legends must work together with The Flash, Supergirl and Green Arrow to kill them once and for all. Meanwhile, Stein figures out, with the help of others, how the team can terminate the Dominators, but is distracted by the aberration he realizes he created in 1987. The crossover starts on Supergirl S02E08 Medusa (I), The Flash S03E08 Invasion! (II) and Arrow S05E08 Invasion! (III).

When a massive timequake rocks the ship while the legends are preparing for their next destination, they must break a cardinal rule of time travel.

The Legion of Doom rewrites history after obtaining the Spear of Destiny, potentially changing the Legends forever.

After Constantine breaks the cardinal Legend rule—you can’t change the past—he, along with Charlie and Zari try to deal with the ramifications without telling the rest of the Legends. Even though Zari encourages them to just fix the problem, Constantine and Charlie are determined to find another way, but only continue to make things worse.

The Legends are determined to find and rescue Rip, but first must focus on locating the Spear of Destiny. Stein thinks he has the perfect person to help but knows involving her will be risky. Meanwhile, Malcom Merlyn and Damien Darhk realize that Thawne is pitting them against each other.

With Ava a wreck, the Legends make a last-ditch effort to keep Sara from being abducted in the first place, even knowing that it will alter the timeline. Sara grapples with a discovery about herself and is shocked when Rory finds her on the mystery planet. Meanwhile, Spooner envisions what her life would be like if she hadn't joined the Legends.

Dr. Nate Heywood, an unconventional historian, makes a shocking discovery. Nate then seeks out Oliver Queen for help to find the scattered Legends. Once reunited, they try to protect Albert Einstein from being kidnapped before the Nazis destroy New York City with a nuclear bomb. Meanwhile, Ray notices that Sara has a mission of her own, which leads them both to face her nemesis, Damien Darhk.

The Legends must devise a plan to retrieve the last remaining fragments of the Spear of Destiny from the Legion of Doom. They find themselves in France at the height of World War I faced with the knowledge that they must destroy the mystical object. They enlist the help of a soldier by the name of John Ronald Reuel Tolkien and find that the Spear is leading them into the heart of the war. Meanwhile, the team must all resist the temptation of the Spear, and the return of a former teammate.

The Legends travel to Nazi-occupied Paris and are surrounded by the Justice Society of America. They discover a time aberration that threatens the JSA, but the JSA doesn't want their help. Meanwhile, Nate tries to prove he should be part of the team.

When a new Time Aberration is discovered by the Legends, they find themselves headed to 1927 Chicago. The Legends quickly realize that they have been set up by Eobard Thawne, Damien Darhk and the newest member of the Legion of Doom, Malcolm Merlyn. While everyone is trying to help fix what they think is the mission, Jax encourages a reluctant Stein to share his secret with the other Legends. Stein is taken captive and Sara must make the tough choice of either stopping the Legion of Doom or saving Stein. Meanwhile, Rory gets an unexpected visitor and is not sure how to handle it.

When Damien Darhk and Malcolm Merlyn try to capture Rip Hunter in 1967, they create an Aberration big enough to draw the attention of the Legends. However, when the team arrives they discover that Rip has no memories of his past due to “time drift” and is just a graduate film student. After trying to convince Rip of who he was, they discover that he possesses an incredibly powerful artifact known as the Spear of Destiny, which the Legion of Doom is after. Ray and Nate realize that the Aberration has also affected them personally making it difficult to help the team. Meanwhile, Rory asks Stein for help and makes him promise to keep it a secret from the team.

When the Legends track Commander Steel to NASA Headquarters in 1970, they learn where Nate's grandfather hid the last fragment of the Spear of Destiny. The team notices a time aberration during the Apollo 13 mission and believes that the Legion of Doom might be involved. As the Legends journey into space to intercept Apollo 13, the Waverider suffers massive internal damage and Ray’s life is left in jeopardy when he is stranded on the moon. Meanwhile, tension grows between Rip and Sara as to who is the leader of the team.

After the Legends defeated Mallus and wiped the final anachronism from time, they find themselves in unfamiliar territory with the Time Bureau. All that changes when Constantine informs Sara of a new magical threat that leads the team to Woodstock. Constantine thinks he knows how to defeat the new threat, but will need the help of the team and their special klepto talents to help with his spell. Meanwhile, Nate and Rory go on an adventure leaving Nate facing someone from his past.

While on a mission to find Ray, Constantine and Nora discover Neron's evil plan. Nate convinces the Legends to think outside the box and suggests a dangerous plan to unite magical creatures and people to save the world.

When Astra and Spooner find themselves as stowaways, they learn that Constantine is still chasing the Fountain of Imperium and find themselves in 1920s Texas. With the rest of the Legends stranded, they come up with a plan to get help by using Rory as bait that will also help reunite him with something that is special to him. Meanwhile, Spooner learns some information about her past that she wasn't expecting.

The Legends learn that Ray Palmer will die because they broke time, causing them to race back to 1988 to try and save his life. When they arrive, they are surprised to learn that young Ray Palmer has befriended a time-displaced baby Dominator putting him in harm's way with the government and the Dominator's mother. New to the ship and missions, Zari must find her place and learn to trust the team. Meanwhile, Stein begins working on a secret project on the ship which makes Rory and Jax suspicious.

A new fugitive is on the loose in 1951 Tokyo and Sara, Zari, Rory and Charlie try to capture it. As Constantine struggles to recover, Ray knows that magic might be the only thing that can save him but must look outside the team for help. Meanwhile, Ava joins Nate and his family for an unconventional Thanksgiving dinner.

Nate is shocked to learn he has powers and accidentally lands himself and Ray in Feudal Japan. Sara, Vixen and Rory agree to find Nate and help him master his powers so he can defend a Japanese village from the Shogun and an army of samurai warriors. Meanwhile, Jax and Stein stay back to help repair the ship and find a secret compartment but decide not to tell the rest of the team what they learn.

The Legends discover a time aberration in 1863 and must fight for survival during the Civil War with Confederate soldiers who have been turned into zombies. With the Civil War outcome hanging in the balance, Jax participates in a daring mission by going to a slave plantation with Amaya. Meanwhile, Sara begins to feel the burden of the decisions she has to make as the leader; and Ray struggles to find his purpose on the team.

When the Legends trace a timequake to President Reagan’s White House, they are shocked to discover their old enemy Damien Darhk is now a Senior Adviser to Reagan. As the team works to uncover what Darhk has up his devious sleeve, Sara struggles with the choice of getting revenge or helping with the team’s larger mission. Thinking that the JSA members could be of help, Amaya and Nate break into the JSA and are surprised at what they find. Meanwhile, Stein tries to prevent his younger self from creating an even bigger time Abberation.

After capturing Rip, he forces the Waverider to crash, leaving the Legends stuck seventy million years in the past. Ray leads Amaya and Nate to recover a vital piece of the ship. In an effort to get the “good” Rip back, Rory suggests they enter Rip’s mind, but what Sara and Jax discover in his subconscious is not pleasant and they must fight evil versions of themselves. Meanwhile, Nate and Amaya continue to get closer, but it could cause serious ramifications.

After the team returns from a mission, Zari finds herself trapped in a time loop that results in the Waverider blowing up over and over again. Zari soon begins to suspect that the answer to stop what is happening might lie hidden among her fellow shipmates' secrets. But in investigating them she starts to understand her place on the team.

When the Legends discover that kids at a summer camp have disappeared, Sara, Ava, Ray and Constantine find themselves as the new camp counselors. At camp, Ava struggles to get along with the kids, but Constantine whips up a potion that helps Sara and Ava bond with the children. Luckily, the team finds clues to the whereabouts of the missing kids, but the battle to save them leaves one member in bad shape. Meanwhile, Rory and Zari are tasked with watching the fugitive and Rory finds a kindship with their "prisoner."

With things getting out of control, Sara and Ava concoct a bold plan to take back the Time Bureau. But when things go awry, Zari and Charlie must work together to discover what Neron is planning. Elsewhere, Constantine is given a tough choice on who to save from Hell.

Being in the vicinity of the Time Masters leaves Rip and Rory incredibly disturbed for very different reasons. Meanwhile, Sara takes over the Waverider, Kendra is reunited with Carter and Snart decides he might be a hero after all.