Onboard Black Manta's sub in the Gulf of Mexico, an imprisoned Lagoon Boy demands to know how Aqualad could have fallen so low. Black Manta comes in and tells his son to send Lagoon Boy along while he has other duties with him. Aqualad agrees and injects Lagoon Boy with a sedative and places him in a transport capsule. Meanwhile, Black Manta tells his son that others demand proof of his loyalty and Aqualad assures his father that he will do whatever it takes to enter the Light.
Aqualad departs, taking his villainous teammates Icicle Jr., Tommy and Tuppence Terror with him. They're wary of the newest villain to join them: Tigress. Unaware that she's actually Artemis undercover, they point out their suspicions but she points out that Black Manta and Aqualad have both vouched for her. Aqualad tells them to focus on the mission and warns them that they're closing on their target.
In El Paso, Impulse comes to see Jaime. Jaime's scarab suggests that they destroy Impulse rather than risk their secret but Jaime switches to his heroic identity and quickly leaves to avoid drawing attention.
In Ivy Town, Karen bumps into Mal and offers to take her out like back in high school. She says that she needs to spend time in Dr. Palmer's lab and he insists on going with her.
Lagoon Boy wakes up and finds himself being transported to the invaders. They discuss the need for teaming with Black Manta and their need for fresh experimental subjects.
In the desert, Blue Beetle demonstrates his abilities but Impulse isn't impressed. Impulse superspeeds around and then tells Blue Beetle to fly up and is surprised to discover that his friend has drawn a large portrait of himself in the dirt. Tuppence suddenly drops out of the sky and lands on Blue Beetle, while her teammates arrive and attack Impulse. After gaining the initial advantage, the heroes rally and realize Aqualad is responsible for the assault. Impulse superspeeds over to him, takes his tracker, and they leave. When the others wonder how they'll find the heroes now, Aqualad says that he has a backup plan.
Impulse and Blue Beetle teleport to Mount Justice to inform Nightwing what has happened. He points out that Impulse brought alien tech into the cave but examines it.
Back aboard Aqualad's flyer, he explains that the first device was a tracking unit that bypassed Mount Justice's security and giving them access to their opponents' headquarters. When they arrive, he swims into the cave and Sphere confronts him. Aqualad uses his palmprint, which is still on file, to bypass security.
The invaders take Lagoon Boy to a lab and he wakes up to discover him next to other imprisoned teenagers.
At Ivy Town, Karen continues her research as Dr. Palmer comes in. Mal still suggests they go out but Karen is too occupied with her work and he finally leaves.
Tigress puts a collar on Wolf to keep him sedated while Tuppence knocks out Beast Boy. Superboy is in the grotto when Tommy and Icicle Jr. attack him, putting on a power nullification collar and shutting down his powers. They then shock him unconscious and prepare to exact some revenge, but Aqualad arrives and tells them that they need Superboy alive.
In the control center, Nightwing realizes that they've been invaded just as the villains attack. They subdue Impulse and Nightwing, and Aqualad orders Blue Beetle to stand down, revealing that he has planted a bomb and holds the dead man switch. If he is knocked out, Mount Justice will be destroyed. Blue Beetle surrenders and they attack another subdual collar to him. Aqualad has his teammates send Impulse and Blue Beetle to the flyer while he leaves Nightwing and Superboy behind since their alien partners aren't interested in non-powered humans and Kryptonian-human hybrids. As he goes, Aqualad tells Nightwing that he'll trigger the bomb if he pursues and leaves with his fellow villains.
As the villains take Blue Beetle to the flyer, the Scarab tells Jaime that it can disable the inhibitor collars. Jaime doesn't want to endanger his comrades but the Scarab takes over and attacks the villains on its own. Aqualad loses the dead man switch but the bomb doesn't detonate. Blue Beetle attacks Aqualad, who blasts open the hero's armor so that Tigress can inject him with a tranquilizer. As they fly away, the villains complain that Aqualad let Nightwing and Superboy live. Overhearing them, Aqualad tells Tigress to do it and she triggers the bomb, blowing up Mount Justice.
In Happy Harbor, Mal sees the explosion and calls Watchtower to request immediate assistance. He then drives to what's left of the mountain and finds the damaged Sphere nearby in the water. It has the unconscious Nightwing, Superboy, and Wolf onboard. Mal wakes them up and gets them clear when Superboy wakes up.
Later at the Hall of Justice, Kid Flash comes to see Nightwing, who explains that Mount Justice's destruction was necessary as part of their plan to infiltrate and destroy the Light's organization. Aqualad earlier injected Lagoon Boy with a micro-transmitter and then passed the tracking information on when he raided Mount Justice. He had no choice but blow up the bomb to maintain his cover, but Kid Flash is angry that he put the others at risk. Nightwing says that Aqualad gave them a warning and they got clear in time, but Kid Flash warns that his teammates are out of control and Artemis, his girlfriend is at risk. He wonders if Aqualad may have become a triple-agent and asks Nightwing if he's sure they can count on their teammate's loyalty.
Aqualad and his team return to base and turn over the captive superheroes. Black Manta takes his son to the communication chamber and introduces Aqualad to the Light committee. The villain assures them that Aqualad has done everything asked of him and they welcome him to the Light and tell him that he will meet their partner.