G. Gordon Godfrey is rallying his audience against the launch of an Earth-Mars comsat, pointing out that they're being invaded by aliens at the same time that they're reaching out to contact them. Wally West is at home in Palo Alto watching Godfrey's show when Artemis comes in to tell him that she's ready. He's not happy that she's going on a mission with Young Justice and blames Nightwing, but Artemis assures him that nothing could go wrong.
Thirteen Hours Later
On a beach at Cape Canaveral, Nightwing tries to revive Artemis but finally declares her dead.
At Mount Justice, Nightwing meets with Mal and Superboy and goes over the status of Impulse and the recently-recovered Roy Harper. Miss Martian arrives with her boyfriend, Lagoon Boy, and Superboy watches them with disgust. As he starts to leave, Artemis teleports in and Nightwing begins the briefing. Gamma Squad will be secretly monitoring the comsat launch to make sure that no one sabotages it, and he plans to go with the team since it's been a while since he's been in action.
Later at Cape Canaveral, launch controller Carol Ferris and Martian Manhunter attend a press conference. Godfrey is up front questioning the necessity of the comsat launch, and both Carol and Martian Manhunter insist that they need allies. Martian Manhunter then flies up into the sky with Superman, revealing that Miss Martian and Superboy are posing as their elders since the League members are off-earth on trial. Superboy isn't happy that they have to pretend or that he has to rely on Miss Martian's telekinesis to make it seem like he can fly.
Nightwing and Artemis watch the land approaches while Lagoon Boy covers the ocean approach. Lagoon Boy is unhappy that Superboy is teamed up with his ex-girlfriend... and unaware that Black Manta's Manta-sub is posting a missile launcher on the ocean floor.
As they wait for launch, Nightwing thanks Artemis for the assist and she admits that she misses the action and likes the rush. Meanwhile, Superboy and Miss Martian return to the bioship and Miss Martian finally reminds him that their breakup was his idea. He complains that she's been abusing her telepathic abilities to destroy their captives' minds, and that he had hoped she cared enough about him to stop. Superboy points out that she tried to tamper with his mind to make him forget how it bothered him and she apologizes, but he wonders if she's sorry that she did it or that she got caught.
Lagoon Boy spots the missile launcher and notifies the others. Nightwing tells him to observe only, but when Superboy describes Lagoon Boy as a rookie, the aquatic teen takes offense and attacks immediately. He puffs up and attacks the Manta-men, while more of their number come ashore to attack. Nightwing has Miss Martian go to help Lagoon Boy while Superboy pilots the bioship on manual, and then engages the ground forces with Artemis. Miss Martian shapeshifts into an aquatic form and swims to help.
Aqualad, still working with his biological father Black Manta, ambushes Lagoon Boy and shocks him unconscious. The Manta-men launch the missiles and Superboy uses the bioship weaponry to blast the docking clamps on the comsat rocket and then shoots the missiles out of the sky. Meanwhile, Artemis realizes that the Manta-men's helmets are equipped to amplify light underwater and uses a flare arrow to blind them.
The Manta-men bring the unconscious Lagoon Boy to the Manta-sub and Aqualad says that their partner will want a specimen. He then goes to help the land team while the other Manta-men continue firing missiles. Aqualad emerges from the water to face Nightwing and Artemis. Meanwhile, Miss Martian sees the Manta-men with Lagoon Boy and prepares to rescue her boyfriend, but Superboy tells her that she has to destroy the missile launcher before a shot gets through. She reluctantly attacks the missile launcher, telekinetically redirecting a missile to destroy it. However, Miss Martian is caught in the blast and knocked unconscious.
Artemis reminds Aqualad of how they were once teammates, but he attacks them while Carl launches a rocket. He fires a mini-missile but Artemis deflects it with a rocket-arrow. In response, Aqualad attacks and stabs her with a water sword. While Nightwing goes to her, Aqualad orders a retreat... only to watch as the comsat rocket blows up on its own. As the villains slip away, Superboy and Miss Martian arrive and can only watch as Nightwing declares Artemis dead.
Aqualad meets with Black Manta and explains that the rocket must have malfunctioned. Black Manta congratulates him, explaining that he secretly put a bomb on the rocket days ago. He's pleased with Aqualad because he didn't take credit for a false victory. When Aqualad wonders what would have happened if he had destroyed the rocket, his father tells him that he would have tested him again. However, he is now satisfied that Aqualad is ready for promotion to the next level of their operation with the Light.
Later, the Young Justice team gathers at Mount Justice to mourn their fallen comrade. Superboy avoids a grieving Miss Martian and vows to Mal that they'll find Aqualad and Lagoon Boy. When Mal wonders where Nightwing is, Superboy explains that their friend went to give Wally the news.
Nightwing goes to a warehouse in Blüdhaven and meets with... Aqualad. Wally is there as well, as is an alive-and-well Artemis. Aqualad reminds them of their plan for him to fake killing Artemis to convince Black Manta that he is on his father's side, and that only the four of them know Aqualad is undercover. He tells the others that he's proven his loyalty and Black Manta is moving him closer to the Light and the group's new partner. Unfortunately, there was nothing Aqualad could do to save the rocket, but he vows to rescue Lagoon Boy.
For the next part of their plan, a disguised Artemis will work with Aqualad. Nightwing gives her a magic necklace that Zatanna has created to disguise her appearance to everyone but the four of them. Artemis kisses Wally and then goes with Aqualad, while Nightwing tries to reassure Wally. However, Wally knows that it will only get more dangerous.