Tess breaks into Watchtower, triggering an elaborate security system that Chloe installed, ultimately trapping the two women inside. Chloe realizes that someone is downloading information from the Watchtower server about the Kandorians, which prompts her to make a drastic move. Oliver confronts Zod and winds up clinging to life with a "Z" scorched into his chest. Clark realizes Zod has given his soldiers super powers.
→ see also Category:Screencaps from episode 9x19
Chloe meets an owner of a coffee stand, he asks her if she always works this late, she answers all night, every night. He asks her what job makes her work so long, she answers it's an NPO that helps people in need. He asks if she's trying to save the world, she answers all night every night. She goes to Watchtower in the elevator. There are new security measures in place in the elevator - fingerprint assessment, voice recognition and passwords. Chloe is admitted into Watchtower and sees a warning message regarding the Kandorian file being accessed. She looks at a box that seems to hold a gun and sees it missing, then she sees Tess with the gun, aiming at her. She asks how Tess found out her secret, and Tess says that Oliver's voice wavered when he heard that watchtower was kidnapped. She distracts her and tries to get her gun back, then Watchtower begins a lock-down. Chloe says she can't unlock it: "Watchtower is in control now".
Clark visits Oliver's office and asks him for help in finding Zod. Oliver suggests using Watchtower, but Clark says he doesn't want this kind of equipment to fall into the wrong hands and he wants to keep Chloe safe. Clark tells Oliver about Zod pretending to be the Blur. He asks Oliver to bring Zod to try to make peace.
Chloe and Tess try to get out by various means, including shooting the metal doors. Chloe finds out that a transmitter was what caused the lock-down. Tess says she didn't bring one; they realize that Checkmate must be the cause.
Checkmate are working on getting the information they got from watchtower and are trying to find its location, it turns out that Stuart Campbell is in charge of the search.
Chloe and Tess are looking for a chip in her bag, and realize that Checkmate might have obtained a lot of information in the short time they had access. They find out that the chip is in Tess' body, and try to get it out but it moves, then Tess tells Chloe that's it's a parasite powered by her body's biorhythms.
At a Kryptonian ceremony with Faora in the middle, Clark arrives and says he's glad they found a way to preserve their culture on Earth. Faora says that Zod has forsaken them because they tried to fit in with humans, and they're waiting to ask his forgiveness. Clark tells her that Zod now has super powers.
Green Arrow breaks into the mansion to find Zod there. Zod offers Green Arrow a chance to join forces against Checkmate. Green Arrow says that if he lets Zod go after Checkmate, he'll start a war. He shoots Zod in his leg with a Kryptonite dart.
Tess and Chloe realize they don't have a lot of air left, Tess says that watchtower is programmed to prevent people from hurting Chloe, and that's why she doesn't let Oliver get close. Tess says that Oliver is not going to leave Chloe since he has a purpose with her. Tess puts ice to her forehead and Chloe realizes that the nitrogen coolant of watchtower can help them blast a hole in the steel. They get out using a desk to smash the frozen steel door.
Clark shows Faora the messages from his father regarding the destruction of Krypton by Zod. She tells him she's pregnant with Zod's child.
Zod manages to remove the Kryptonite dart and downs Oliver by burning a large 'Z' onto his chest, and he then leaves. Amanda Waller tells Campbell to stop looking for Tess since they found the Aliens, but he refuses to stop. Chloe and Tess are in Met Gen looking for a way to deactivate the chip. Faora tells her people she wants to have peace and Checkmate breaks in. Oliver tells Clark that Checkmate is after the Kandorians. Chloe tells Tess that the only way to remove the chip from her body is to stop her heart so that the chip stops moving. This will kill Tess, but Chloe promises to revive her with Atropine. Chloe performs the operation, and then shocks her with the paddles to bring her back to life. Chloe warns Tess not to say anything about her or her friends, otherwise next time Chloe won't rescue her.
Waller talks to Faora and Zod attacks Waller, Zod talks to Faora about their past, and says she betrayed him. Faora tells him that she knows that he sacrificed one world for his ego. Zod tells her she knows nothing about sacrifice, but she tells him she knows more about it than he ever will. He chokes her to death after she refuses to kneel before him. He sees the flowers in her hand and her other hand on her stomach and realizes she's pregnant, he listens to the fetus' heartbeat fading away.
Waller says that they're at war and the Black King is missing, that Zod destroyed their Metropolis field office, and orders Stuart to contact the UN. She and Campbell see everyone dead, and then Zod appears and starts burning everything.
Chloe visits Oliver in the hospital, where Clark is outside. They see the castle burning on the TV news, and she tells him that there is movement in the fortress.
In the fortress, Zod lies to his soldiers that the humans killed Faora and her unborn child. Clark arrives and tells them it's a lie, and that he left her alone with Zod. Zod says that Clark helped Waller. Clark tries to talk to Vala saying that she, more than anyone, knows that her sister Faora wanted peace. She says that the humans will not allow peace and sides with Zod. Zod says that all humans will kneel before him, and he gives Basqat a nod and they all fly away.
- Tom Welling as Clark Kent
- Allison Mack as Chloe Sullivan
- Erica Durance as Lois Lane (credit only)
- Cassidy Freeman as Tess Mercer
- Callum Blue as Zod
- Justin Hartley as Oliver Queen/Green Arrow
Special Guest Star
- Sharon Taylor as Faora
- Crystal Lowe as Vala
- Adrian Holmes as Basqat
- Jonathan Lloyd Walker as Paul Brenner
- Ryan McDonell as Stuart Campbell
- Joe Maffei as Frank
- Paul Duchart as ER Doctor
- Giles Panton as Agent
- Kate Crutchlow as Checkmate Medic
- Sacrifice is commonly known as the practice of offering food, objects, or the lives of animals or people to the deities as an act of propitiation or worship.
- It also means doing without something or giving something up.
- The term is also used metaphorically to describe selfless good deeds for others or a short term loss in return for a greater gain, such as in a game of chess.
- Chloe sacrifices Watchtower so that she and Tess can escape.
- In order to gather the decreasing support of his fellow Kryptonians and to make it look as if The Blur is a murderer, Zod sacrifices his wife Faora and their unborn child.
- Oliver sacrifices being burned by Zod to get information from him.
- Faora sacrifices herself and her child to stand up to what she believes in.
- Tess sacrifices herself to stop Checkmate from finding her and Chloe.
- Antagonists: Zod, Amanda Waller, Stuart Campbell and Checkmate.
- This is the final appearance of Amanda Waller on the show. While presumed deceased, character's fate and storyline was left unresolved as the character was going to be used in the Green Lantern film, which was in production during season 10. A similar situation later happened on Arrow when studio politics resulted that show’s versions of Waller and Deadshot being killed off due to their use in the Suicide Squad film. 
- Lois Lane does not appear in this episode. This is the final episode of the entire series not to feature Lois, as she will appear in the final two episodes of Season Nine and all 22 episodes in Season Ten.
- This episode marks Justin Hartley's writing debut on the series; and as well as the first time a series regular has written an episode.
- Zod and Oliver finally meet.
- When the original Faora escaped from the Phantom Zone in Bloodline, she mentioned that she and General Zod were unable to have children, so they decided to create Doomsday. However, in this episode, their replicants either proved that they would have been able to have children together sometime in their lives before some incident happened that prevented either or both to have children later since their replicants were able to procreate, or, that the clones simply did not have whatever problem the original Zod and Faora had with having a child.
- Chloe's password to Watchtower is 051409. This is the original airdate of the episode Doomsday and the supposed date Jimmy's death. However, in Savior, the date was shown as September 25, 2009, which took place three weeks after the events of Doomsday. So, Jimmy's death actually would've taken place in September, not in May. Thus, this was either a continuity error, or an in-universe coincidence.
- This is the second time Tess has died on the show. Both times were at the hands of Chloe Sullivan. The first time was in Pandora, an alternate future under Zod's rule. This time, Chloe killed Tess to save both their lives from Checkmate, and she was then resuscitated with atropine.
- Major Zod threw Amanda Waller against a car's windshield in a very similar manner that a superpowered Lex Luthor threw Lionel Luthor against his limousine windshield in Vessel.
- This episode marks Zod's promotion to "General".
- When Zod crouches over Faora's stomach, Faora can be seen moving her eyelids.
- The coffee vendor was last seen in Warrior, where he gave Alec Abrams (as Steven Swift) his first cup of coffee.
- Chloe borrowed Oliver's funds to upgrade Watchtower's security in Charade.
- Stuart Campbell was looking for revenge on Tess for what she did to him in Pandora.
- Faora and Vala were last seen in Conspiracy.
- It is notable that the clones of Zod and Faora were able to conceive a child since it was stated by Faora in Bloodline that she and the original Zod were not able to have children, leading them to create Davis Bloome.
- This is the 7th and final appearance of Faora (clone). She is tied with Dr. Harden, Adam Knight, Grant Gabriel, Gina, and Jeff Hage as the 10th most frequently seen recurring characters in the series after Jor-El, Nancy Adams, Brainiac, Emil Hamilton, Ethan Miller, John Jones, Nell Potter, George, and Helen Bryce. Faora, Dr. Harden, Adam, Grant, Gina, and Jeff are the most frequently seen recurring characters in the series who are tied with each other in the number of episodes they appeared in.
- Basqat was last seen in Pandora.
- Amanda Waller, Agent Brenner and the Checkmate organization were last seen in Checkmate.
- Clark showed Faora an entry of Swann's journal mentioning Zod destroying Krypton. The journal was last seen in Veritas.
- The Book of Rao was seen in a drawing (by Faora), yet was last mentioned in Upgrade and seen in Kandor.
- The Coffee Vendor was also in Infamous as the newspaper stand worker, last seen in Warrior.
- The Red Queen was mentioned by Waller. She was first seen in Charade.
- Waller mentions Maxwell Lord (The Black King). He was first seen in Charade.
- This episode marks the 17th appearance of Clark's black Blur outfit, which he wears frequently throughout Season Nine and in the Season Ten premiere Lazarus.
- Checkmate Headquarters (final appearance)
- Arctic Circle
- Clark: I let myself in.
- Oliver: Terrific. You, uh, hop up to the helipad or just superspeed past security, Clark?
- Clark: I used the elevator.
- Oliver: How human of you.
- Chloe: (to Tess) I knew you were the Kandorians' lapdog, but I didn't realize you were Zod's little bitch, too.
- Amanda Waller: We can't afford to make a mistake with the Red Queen so close. Don't make me regret putting my little White Knight back in play.
- Zod: Why don't you join me against our common enemy?
- Green Arrow: Well, I'm flattered, but if I let you go after Checkmate, you'll start World War III. (aims his bowcast at Zod) It's not an option.
- Zod: Your conviction is admirable. But you can't possibly think you're faster than me.
- Green Arrow: I've always been taught to favor accuracy over speed.
- Chloe: We got three minutes of air left. You think Checkmate will find us before then?
- Tess: Asphyxiation or firing squad.
- Chloe: Damned if we do, damned if we don't.
- Tess: Just damned. I just wanted to save the world.
- Chloe: That's funny. Last time I checked, you were just trying to get rid of everyone in it.
- Amanda Waller: Our field offices were just leveled by the one you call Zod.
- Faora: We knew nothing about this. Zod is acting alone. We stand apart. We only want peace.
- Amanda Waller: Dozens of my agents are dead. We are way past peace.
- Faora: Then we will help you stop him.
- Amanda Waller: Defecting means betraying your own kind.
- Faora: I'm only betraying one.
- Zod: I've trusted you for so very long. Depended on you across time and space. But in your eyes, I just see contempt. I see betrayal. Now, why would you turn your back on me? I shared my bed with you.
- Faora: I didn't turn my back on you. You turned your back on us when our only crime was trying to forge a life for ourselves on this planet.
- Zod: If I ever learned that insurrection had spread across my ranks, if I ever discovered that my men had aligned themselves against me, I would raze this planet. I would burn it to the ground till the last ember went cold beneath my boot! Now only I will lead us to the next age. All will follow Zod.
- Faora: You already sacrificed one world for your ego.
- Zod: You know nothing of sacrifice.
- Faora: I know more than you ever will.
- Clark: Vala, if there's anyone who really knows what your sister wanted, it's you. It was peace, Vala. She wanted peace.
- Vala: No. Zod's right. The humans will never allow Kandor peace.
- Basqat: They will hunt us to the last man. But they will fail, for we shall never be defeated. We will follow General Zod to the ends of this Earth.
- Zod: Krypton will rise again. And all humankind will kneel before Zod.
- Clark: I'll never let that happen!
- Zod: You won't be able to stop us.
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