Kai's investigation of a Vermillion Warrior Helmet leads him to discover that Krux is alive and well in Ninjago, living under an assumed identity. Meanwhile, as the Vermillion Warriors go on a kidnapping spree, Lloyd struggles with his role as master-in-training and Nya does her best to reboot Zane, who was knocked offline in his first battle with the Vermillion.
After Cyrus Borg is kidnapped and Zane damaged, the ninja are down one master and one ninja. Master Wu is becoming weaker by the second and the Forward Time Blade is still in the hands of Acronix and Krux, the Time Twins. Kai goes to the museum to find out the origin of the helmet they obtained from the Vermillion while the others try to get Zane working and find out what knocked him out. On the screen, they see a green blur hit Zane, then take off with Borg. They try to get super slow motion working, but then it crashes, forcing them to restart the program. Meanwhile, Acronix and Krux discuss how to control thousands of Vermillion in Krux's lair. Explaining to his brother that he's had forty years to develop his plan, Krux reveals three Vermillion generals, Raggmunk, Blunck, and Machia, all who use their telekinetic abilities to control the Vermillion via a Hive Mind.
Back in the Samurai X Cave, the ninja get the slow-motion working and find out that Acronix used the time blade to turn into a blur, and he takes off with Borg. Nya thinks Borg saw someone different as well, and soon after they see Dr. Saunders looking at Zane with an evil smile on his face. Realizing that Dr. Saunders is working with Acronix, they realize Kai is walking "right into that snake's nest" at the museum.
Meanwhile, Kai looks at the paintings in the museum and finds the painting of his parents. As he says he wishes they were here, he remembers to when his parents introduced him to a newborn Nya. While looking, Dr. Saunders tries to hit him but Kai turns around before he can strike. Kai asks for the helmet's origin, with Dr. Saunders explaining it could be a cheap knockoff and lets him look around while he looks at it.
On the streets of Ninjago City, Nya, Cole, and Jay rush to the Ninjago Museum and find the Vermillion kidnapping people again, so Cole and Jay try to stop the kidnapping but fail.
Dr. Saunders tells Kai that it is near closing time so he needs to go. Just as he is about to leave, he sees the painting that Acronix and Krux are in with the helmet. Just as Dr. Saunders tries to say to Kai to leave, his fake mustache gets caught on a statue and comes off, accidentally revealing himself as Krux. They battle for a short time until Krux tells Kai about hisparents: "Oh, they were heroes, heroes for our side!"
Nya arrives but were attacked by snakes in an exhibit. She kills them and helps Kai fight Acronix and Krux until they flee with the Time Blade along with Borg.
Then, everyone goes back to the cave to reboot Zane.
Kai's vision from the painting of his parents is not a flashback, but rather, what his mind makes of the image. This would explain why baby Nya's clothing resembles her Water Ninja attire despite her not being the Water Ninja until recently.
The ninja split up in this episode, Lloyd stays at their new base to watch after Master Wu, Kai goes to the museum to find answers about the Four Weapons Blacksmith print on the helmet, and Nya, Jay, and Cole go to the Samurai X Cave to reboot Zane and find the answer to his injury.
Kai finds out Dr. Saunders is Krux, Acronix's brother.
Kai also learns about his parents being "traitors" from Krux.
Nya, Jay, and Cole mention having gone on field trips to the museum. While it's unclear from the episode whether they were referring to their time as teachers at Wu's Academy or their own education in their younger years, Tommy Andreasen later implied it to be the latter.
According to Acronix, he and Krux were born three minutes apart, with Krux born before Acronix.