Young Justice has gained and lost members, and works closely with the Justice League. Now, an alien race has launched an invasion of Earth from Rann using teleporters, and only Young Justice can travel there since the Justice League has been outlawed on the planet.
On Rann, Beast Boy, Miss Martian, and Superboy team up with Adam Strange to locate the home base of the Kroloteans and stop the invasion at its source.
The Team and the Justice League continue to hunt the Kroloteans that have invaded Earth-but the aliens have help from an extremely unexpected source.
While Superboy and Blue Beetle battle Intergang, Nightwing and company try to salvage the soul of a former comrade fallen from grace.
Jaime Reyes searches for a missing friend, while Miss Martian, Batgirl, Bumblebee and Wonder Girl return to Bialya to discover what lies beneath.
Impulse, a speedster from the future who claims to be the Flash's grandson, arrives at Mount Justice and is eager to meet his relatives. Meanwhile, Red Arrow and Cheshire track down Roy Harper.
Artemis rejoins the team to defend a critical satellite launch. But will her first mission back also be her last?
While Young Justice go on with their lives, Green and Red Arrow explain to the recently-discovered Roy Harper that he has been a prisoner for eight years after being cloned, and he sets out to take revenge on the man responsible.
Black Manta has a new mission for his son: a mission that should prove once and for all exactly whose side Aqualad is on!
The team goes on a mission to rescue its missing comrades, and discovers that the Reach is allied with the Light and responsible for the abduction of dozens of teenagers... and plans to use Blue Beetle to further their invasion plans.
The Team is trapped inside the Hall of Justice for a cage match against a brutal alien gladiator!
When the Reach forms a devil's alliance with Lexcorp, Robin leads a squad undercover to investigate.
In revenge for her telepathic attack on his son, Black Manta goes after Miss Martian.
Four of The Reach's teenager abductees break out of STAR Labs when they grow tired of the endless experiments on them. When Blue Beetle tracks them down, however, they agree to go back only find the lab under attack by a hugger android.
Rather than let Earth fall under the control of The Reach, the alien warlord Mongul brings his planetary-sized mobile weapons platform to destroy the planet. To stop it, Young Justice and the Justice League must join forces to stop it... and receive help from an unexpected ally.
Black Manta gives Miss Martian twenty-four hours to live, but that may be more time than Aqualad has with Sportsmaster and Cheshire on the hunt for his head!
Luthor convinces the former Reach test subjects to sneak aboard Warworld and rescue the captive members of Young Justice... providing a distraction so that The Light can recover a vital piece of equipment. Meanwhile, public opinion about The Reach begins to change.
The team embarks on a desperate endeavor to free Blue Beetle.
The Light call a summit with the Reach to discuss how their plans are advancing. As the tensions between the two groups begin to come to the fore, Ra's al Ghul notices the glamour charm on Tigress's neck and exposes her as Artemis, leading Deathstroke to execute both her and Kaldur. However, a hologram of Aqualad then plays which reveals to the Reach the extent of the Light's manipulations, leaving their alliance in tatters. Aqualad and Artemis suddenly rise, and as 'Deathstroke' turns out to be a disguised Miss Martian, the Team and Kid Flash make their entrance, leading to an all-out battle. In the midst of the chaos, the Reach ambassador and the Brain are captured, while Aqualad defeats Black Manta and Black Beetle mortally wounds Ra's al Ghul. However, Ubu rescues Ra's (pledging that he will be revived), Black Beetle escapes with the Reach Scientist, and Vandal Savage summons Klarion to elude the Team. In the aftermath of the battle, Nightwing insists that Aqualad take over leadership of the Team, while Savage ousts the League from the War World by defeating Black Lightning, Black Canary and Captain Marvel; then uses it to flee into space. On Earth, the League present the public with proof of the Reach's duplicity, and Black Beetle assumes control of the alien fleet, swearing to destroy the Earth now that it is of no further use to them and before the Green Lantern Corps and Guardians of the Universe arrive.
On the verge of finally ending the alien invasion, the team discovers the price of victory may be the entire planet Earth!