"Legends of To-Meow-Meow" starts with Charlie going back in time to track down a former friend, who appears to be a real-life leprechaun. Charlie explains to her friend that she's trying to lay low and stay off the Legends radar. Ray, Mick, and Nate walk in and Charlie shapeshifts into Marilyn Monroe. The trio shoots the leprechaun, killing him.
Back on the Waverider, Charlie asks Gideon what happened with the group and Gideon informs them that the time break caused the Legends to turn into the "Custodians of the Chronology" and they now shoot on sight. Charlie tries to shapeshift into Sara to wrangle the group into order but it's revealed that Sara's died.
They try killing Charlie but she's able to make it off the Waverider with Zari — who's still a cat — in tow. Charlie arrives at the Time Bureau and shapeshifts into Gary. Before long, Hank Heywood confronts Gary because everything at the Time Bureau is going to "hell in a handbasket." Charlie's able to find Constantine, who's been incarcerated for months.
Constantine's able to change Zari back into a human and she's informs the group that Constantine broke time when he changed his past with Desmond. Zari explains that they need to go back in time and fix Constantine's past with Desmond but John and Charlie refuse. They decide to go back to Woodstock and save Sara from her death instead. Zari tries stopping them, but is turned back into a cat by Constantine.
On their way out, Charlie and Constantine are bumped into by Mona, who offers to help them out because she's against the ways of the Custodians as well. The trio ends up recruiting Ava to their squad after telling her that Sara is alive in the right timeline.
They're making their way out of the Time Bureau when they bump into the Custodians. After a brief fight, Ava, Zari, Charlie, and Constantine are able to escape and they go back in time to save Sara at Woodstock. They manage on saving their captain, but when they go back to present day, they find out that Nate, Mick, and Ray are now dead instead.
In the new timeline, Sara, Ava, and the human embodiment of Gideon have joined together as the Sirens of Space-Time. Charlie pretends to be Amaya and joins the trio in their new crime-fighting group. The quartet leaves for a mission and on their version of the Waverider, they tell Charlie that they also kill all of the anachronisms. Charlie tries sneaking off to get help from Constantine and Zari, but the trio soon finds out.
Charlie's able to escape and gets back to the pod with Constantine and Zari, who's still a cat. The trio goes back to Salem in an attempt to save Nate, Ray, and Mick from the Fairy Godmother. They save the guys and go to head back into the present timeline again only to find that Zari's been changed from a cat into a ventriloquist dummy. Charlie and Constantine go out on the Waverider to find out that the entire team has been morphed into the puppets.
We then see a quick sequence of the team continues to go back in time, trying to fix the timeline. Each time someone new ends up dead before they eventually get everything fixed. Charlie, Zari, and Constantine are chatting about their success when John suddenly passes out. The group realizes that Constantine will eventually end up killing himself if he doesn't go back and fix the timeline.
Constantine and Zari head back again to try and right the timeline and try tracking him down to kill him. In the new reality, they think Constantine is a shapeshifter. Charlie reveals herself to be the shapeshifter in an effort to save John's life. She asks the group what happened to them to make them obsessed with murder.
In 2018 New Orleans, correct-timeline John fixes the timeline, ensuring Desmond is sent to Hell after all. Charlie, Zari, and John arrive back on the Waverider to find the rest of the time tying up the possessed Victor Stein doll from last week's episode.
In the correct timeline, Mick bakes Ava a batch of snickerdoodle cookies and the two bond over the manuscript for Mick's novel.
Constantine bulls Sara aside to tell them of the timeline mishaps. Constantine unveils that's he's being chased by the demon Neron and asks Sara for their help.
Hank Heywood is out golfing when it's revealed that he's been receiving orders from Desmond, who has been physically altered.