The League holds a press conference at the Hall of Justice in Washington and introduces their five new members: Dr. Fate, Plastic Man, the Atom, Icon, and Red Arrow. Inside, Young justice is watching the newscast along with their newest member, Rocket, Icon’s sidekick. Icon isn’t happy that she has been assigned to the “junior” undercover team, but is happy to be working with Aqualad. The others comment about how Red Arrow has finally graduated to the adult team and figure that he’ll be the first but not the last.
After the ceremony, Batman and Black Canary take the five members to the teleport to go to the initiation party at the Watchtower satellite. They discover that Young Justice has left without warning.
Young Justice is taking Miss Martian’s bioship to the Smokey Mountains. Robin explains that he hacked the League computers and learned that Cheshire was spotted at a private airfield, carrying the briefcase that she took in New Orleans. They explain to Rocket that the villains behind the Injustice League are still at large and Cheshire works for them, while Kid Flash complains about how Artemis was the one who lost them the briefcase in New Orleans.
The team finds the remains of the plane, which has crashed in the mountains. Cheshire emerges from the shadows and says that she brought company to deal with the teen heroes. The Riddler, Shimmer, Mammoth, and several mercenaries armed with Apokolips weaponry move out and activate force field pylons, sealing in the heroes. Zatanna summons a storm for cover and the fight is on. Superboy puts on Luthor’s last shield to access his full Kryptonian powers and attacks the pylons, while Artemis battles her sister Cheshire. The fight goes back and forth, and Robin notices that Superboy is using Kryptonian powers that he isn’t supposed to have. When Superboy goes berserk and attacks Mammoth, he inadvertently creates a landslide on Artemis. Cheshire rescues her sister and admits that she doesn’t want her dead, just defeated. As she slips away, Robin and Zatanna capture Shimmer and the Riddler and the team destroys the force field pylons.
When the team returns to Mount Justice, even Batman has to admit that despite the fact that they disobeyed orders, they recaptured three villains and revealed that Hugo Strange is part of the conspiracy at Belle Reve. Amogn the villains’ equipment are nanotech devices equipped with unidentified biotechnology. As the League members depart for Watchtower, Icon notes to Rocket that she seems to have found a team that suits her.
Once the adults leave, Robin voices the suspicion that someone on the team told the villains where to find them. When Rocket wonders what they’re talking about, the team explains that there was supposedly a mole within their team. As Aqualad asks Superboy about his recent berserker rages, Superboy gets a secret signal from Luthor asking him to meet in Santa Prisca to get more shields. Superboy tells his teammates that he has personal business and turns to leave.
Later, Superboy takes Sphere to Santa Prisca. Luthor is waiting for him along with his fellow villains Queen Bee, Sportsmaster, and Blockbuster, as well as his bodyguard Mercy. Luthor explains that Bane is letting them use his island of Santa Prisca as a base of operations in return for “considerations.” A helicopter arrives and two people get out: Cheshire and Artemis. Superboy is surprised to see his teammates, but she explains that no one on Young Justice trusted her so she has decided to side with her father and sister. Superboy is even more surprised when Miss Martian arrives in the bioship. Ashamed, Miss Martian complains to Queen Bee that she thought her betrayal was supposed to be a secret. Queen Bee tells her to keep her promise and Superboy agrees to work for them in return for more shields. Luthor doesn’t believe him and gives the command phrase, putting the clone into a mental fugue. Artemis wonders what they want them to do and Sportsmaster tells her that she’ll be serving at his side.
Earlier, rather than leave to meet Luthor, Superboy confessed to his teammates that he was using Luthor’s shields to obtain full Kryptonian powers.
Luthor tells Blockbuster to bring the immobilized Superboy with them so that Queen Bee can reprogram him at her leisure. However, Artemis begins shooting at the villains.
After Superboy’s confession, Artemis admits that her mother is Huntress, an ex-super villainess, and Sportsmaster and Cheshire are her father and sister, respectively. Kid Flash realizes that she messed up the New Orleans family because of her loyalty to her family. Robin admits that he knew all along who her family was, but that he knew that ultimately she was with them.
Artemis reveals that her mother is Huntress, an ex-con, and Sportsmaster and Cheshire are her father and sister. Kid Flash realizes that she betrayed them because of her family connections, and Robin admits that he knew all along but also knew that no matter who her family was, she’s one of the team.
Queen Bee orders Miss Martian to dispose of her rebellious teammate, but instead she telekinetically deflects Blockbuster’s attack on Artemis.
Miss Martian tells the team that Queen Bee is blackmailing her by threatening to reveal her true White Martian form. She reveals what she really looks like to the team, but Aqualad assures her that they value her for who she is, not what she looks like. Superboy takes her hand and admits that he knew her true form months ago when they mind-melded in Bialya. He decided to let her wait until she was comfortable telling him her secret.
Superboy reveals that Miss Martian has telepathically removed the programmed commands rom his mind. When Superboy tries to go after Luthor, Blockbuster opens him while Bane and his soldiers open fire. Sphere opens fire on them and Cheshire and Sportsmaster attack Artemis. The rest of the Young Justice arrives to help their teammates and Bane goes after Robin. Aqualad tries to stop Luthor but Mercy stuns him. When Rocket tries to stop the helicopter, Luthor fires missiles at her, forcing her to drop back. By the time she recovers Aqualad, calls her back to help with the other villains.
Kid Flash races to help Artemis against Sportsmaster but finds himself outmatched. Meanwhile, Zatanna creates an army of Robin images, letting him take down Bane. Miss Martian goes to help Superboy, helping him against Blockbuster long enough for Aqualad to stun the villain. Zatanna then creates a pit of mud, trapping Sportsmaster. He calls to Cheshire for help, but she abandons her father and slips away while Artemis kicks her father unconscious and gives his mask to Kid Flash as a souvenir.
On the Watchtower satellite, Batman is analyzing the nanotech that they took from the villains. Red Arrow comes in to invite him to the initiation party... and slips one of the nanotech control devices onto Batman’s neck. He then leads Batman into the main chamber where the other mind-controlled heroes have assembled. Batman activates the teleporter and beams aboard the mastermind of the entire scheme: Vandal Savage. The heroes bow before their new master while Red Arrow, freed from the mind control, realizes that he has been the mole all along.