Hal and Kilowog are aboard the interceptor in the Frontier and receive a transmission from the Guardians. Appa accuses Hal of treason and theft, but Hal interrupts to inform the Guardians that the mysterious Red Lanterns have been killing Green Lanterns along the frontier. Appa believes that Hal is making a fake claim to cover his own actions, but Kilowog testifies on his friend's behalf. He recommends that he and Hal return with the interceptor, gather more Green Lanterns, and then return to take on the Red Lanterns.
The Guardians tentatively agree, but the conference is interrupted when Aya detects an unmanned killer-drone in the vicinity, one bearing the same insignia that Razer and Zilius wore. Hal breaks off communication with his superiors and charts an intercept course for the killer-drone. Back on Oa, the Guardians worry about what will happen if the truth comes out despite what is written in the Book of Oa. Appa notes that since they won, they wrote what is contained in the book.
Hal ignores Kilowog's advice to return to Oa and fires on the drone. It returns fire, hitting the interceptor repeatedly, but Hal finally takes the ship through an asteroid and emerges from the other side to destroy the drone. Shyir deduces that if the Red Lanterns have a killer-drone, there must be more to them than two killers. Hal agrees and sets course for Oa to gather the Corps. However, the ultra-warp drive fails to activate and Aya reports that there is a hairline crack in the warp coil, caused by the killer-drone's return fire. Hal figures that it's for the best because the Guardians wouldn't have done what needed to be done. Shyir collapses from his injuries and Kilowog warns Hal that without medical treatment, their comrade will die. Shyir suggests that they go to his home colony on a nearby planet and the others agree. As the interceptor heads for the colony, the heroes are unaware that the killer-drone attached a tracking device to the hull.
Zilius and Razer board Shard, the remainder of their leader Atrocitus' homeworld. Atrocitus berates them for letting three Green Lanterns escape and Zilius blames Razer. Razer warns that the Green Lanterns they fought were better trained than the Frontier Lanterns they had killed, but Atrocitus is unimpressed. He warns his minions that if the Guardians learn of their existence, they will destroy Shard just as they destroyed the rest of his homeworld. Razer receives the last transmission from the killer-drone, confirming that it fulfilled its mission to attach a tracking unit and that they can now hunt down the green Lanterns and destroy them.
At the colony world, the interceptor lands and begins repairs while Biara, Shyir's wife, tends to his injuries. Shyir informs Hal and Kilowog that he's an engineer and his wife is a geologist, and that she mapped out the volcanic tunnels to provide the colony with power. Shyir's daughter Amala comes out to see her father and after a brief reunion, Biara takes her daughter to bed. Kilowog goes to view the planet and tells Shyir that it reminds him of his homeworld, Bolovax Vik, and Shyir remembers that the planet was destroyed. He offers his condolences and Hal, startled to learn this news about his friend, starts to ask him what happened. Kilowog tells him to focus on their mission, and Aya announces that she's found the tracking unit on the hull. Hal destroys it, but Shard descends toward the planet and Atrocitus drops a fortress unit on the colony's nearby volcano. Atrocitus tells the colony that they are now under his "protection" and that they can either turn over the Green Lanterns in an hour or be destroyed.
Shyir is willing to turn himself in for the good of his people, but Kilowog warns him that Atrocitus will destroy the colony once he has what he wants. Hal vows to fight to the end, convincing Shyir, and the three Green Lanterns prepare to charge the fortress. However, Biara says that she has another way for them to get to it.
One hour later, Atrocitus tells Razer to begin the destruction sequence to test his loyalty. Razer hesitates, protesting that the colonists are innocent, but Atrocitus says that they have to make an example of what happens to those who refuse to help them. When his leader accuses him of weakness, Razer insists that he isn't weak and activates the destruction device for the greater good. Hal arrives outside the viewing portal and taunts them, and Atrocitus and Zilius fly after him while Razer watches the bomb. Hal easily defeats Zilius, but Atrocitus engages him atop the fortress and overwhelms Hal, swearing vengeance on the Guardians and the Corps.
Kilowog and Shyir follow Biara's map of the tunnels and approach the fortress from below. They cut through the floor and get to the bomb, but Razer opens fire on them. Meanwhile, Atrocitus' rage and experience prove superior to Hal's spirit and the Red Lantern smashes the Green Lantern repeatedly.
While Kilowog holds off Razer, Shyir tries to disarm the bomb. As they fight, Razer insists that it's the Guardians who are destroying worlds, and blames them for his actions. Kilowog points out that the only one destroying a world now is Razer and asks for his help. Razer insists that he won't fall for their lies, but hesitates long enough for Kilowog to knock him out of the fortress. Rather than pursue the fight, Razer flies away when he hears that the bomb has thirty seconds until detonation.
Atrocitus finally stuns Hal, dropping him onto the fortress, and then flies to the orbiting Shard with Zilius. Hal, recovering, flies after them.
When the countdown reaches 0, a laser trigger fires to activate the bomb. Shyir blocks it with his power beam and tells Kilowog to leave before it's too late while he buys his people time to escape. Kilowog says that it's been an honor and leaves. Razer returns and tells Shyir that he was stupid to stay when there was no hope, but Shyir says there's always hope. He tells Razer that he can tell the youth isn't bad and that he should escape before the bomb detonates. Razer flies away as Shyir's power ring finally gives out and the bomb detonates.
In space, Hal looks back and see the planet blow up, and the blast wave sweeps over him.
On shard, Atrocitus views the destruction with satisfaction and tells Zilius that he was wrong about Razer. The Red Lantern leader then announces that with the destruction of Oa's Lanterns, they can move on and conquer the galaxy.
Hal recovers from the blat and looks for Kilowog. Razer attacks him amidst the debris and informs Hal that Kilowog and Shyir are gone. Hal finally defeats him and Razer tells him to finish it. The Green Lantern almost kills Razer, but then says that he's going to live with the consequences of what he's done and make up for what he caused to happen. Razer flies into a rage, calling Hal a coward, and Hal strips him of his Red Lantern ring, causing the youth to revert to normal. Kilowog arrives with the colonists, having lifted them off the planet at the very last second. He asks for Hal's help, but Aya arrive and transfers green energy to the transport construct to keep the colonists safe. Hal and Kilowog watch as Shyir's ring flies away to Oa to receive a new Green Lantern.
Later, the Green Lanterns take the colonists to a new world. Biara tells Hal and Kilowog that they will name the new planet after her husband, and Hal assures Amala that her father was a brave man. As Biara leaves with her daughter, Kilowog tells Hal that he was able to save the colonists, the same thing he would have done for his people if he could. As the two Green Lanterns leave in the interceptor, they wonder what to do about Razer, depowered and held in a cell aboard the interceptor.