Clark, unknowingly, exposes himself to Zod when a virus is released on Metropolis that turns its residents into zombies.
Zod and his soldiers release a virus in the air that transforms the humans into zombies. While finding a way for reversing the effect, Dr Hamilton finds out he needs blood from another Kryptonian to counteract the virus. So Chloe asks Clark to donate a bit of his blood even when that risks Clark from being discovered by Zod.
After Tess is admitted to the hospital showing plague-like symptoms, Clark has Dr. Hamilton investigate the cause with a Disease Control specialist. Clark overhears that Tess was at the Daily Planet when she began to show symptoms, so he speeds to the Planet to rescue Lois in the mist of a zombie-attack against the city. In a battle with multiple zombie attackers, Lois is bitten. Clark then volunteers his blood to Dr. Hamilton, who discovers that the virus was created from Kryptonian enzymes, so the doctor needs a cure. It is revealed that the virus was used as a ploy to draw out 'the Blur', as one of Major Zod's men realize that he is also Kryptonian. Based on the House of El symbol the Blur brands around town, Zod believes that Jor-El is on Earth, and has harnessed the power from Earth's yellow Sun for himself which increases the frustration with Zod as to why the Kryptonian has super powers while he and the rest of his followers don't. Yet still, neither Clark nor Zod are aware of each others existence. Meanwhile, Oliver decides to burn his Green Arrow outfit, and give up trying to be a superhero due to his guilt over recent events.
- Clark awakes alone in Watchtower. He pulls a piece of surgical tape off his arm to reveal bruises and a puncture mark. His phone rings across the room and, as he goes to get it, he passes a needle that had been dipped in kryptonite used to penetrate his skin. His phone has a text message from Oliver: "I lost her". Clark quickly ventures out into what he sees are the deserted streets of Metropolis and makes his way to the Daily Planet. Upon arriving, the basement is in disarray and music is blaring in the background. He calls Lois's name a few times before seeing her in the back of the room. But when she turns around, she utters an animal-like growl and charges at him, and her face is horribly disfigured.
12 hours earlier
Clark is listening to the police scanner at the Daily Planet but quickly turns it off when he sees Lois arriving. Lois is delighted to have Clark back as her partner but is also a bit irritated by the Blur not contacting her. Lois gets news of a fire but Clark is able to rush off and take care of it under the guise of getting them a quick cup of coffee. Lois is marvelling at the Blur having so quickly put out the fire while Clark tries to wipe a soot-mark off his hand. They then receive a report of a high speed motorcycle chase and Clark uses his Arctic breath to cool Lois's coffee to distract her while he rushes off and stops the biker as the Blur, only to find it's Oliver. They argue and Oliver mocks Clark, referring to him as God. Clark admits he was wrong about how he dealt with Davis but Oliver throws it back in his face, asking why he feels he has to plaster his symbol around the city. Oliver then speeds away past a cop car, which turns around to chase him.
Tess is at the mansion, going over the satellite photos of the Kryptonian symbols that have been found around the world. Two of her security guards enter and she lambastes them about not finding the new Earth-fallen Kryptonians. They are interrupted by a loud noise in the hallway and find a security guard unconscious. The power goes down and another security guard is attacked by a crazy-looking person who crashes through a window. Tess attempts to call for help but has to fight off several of the crazy people, one of whom bites her in the struggle.
Lois and Clark arrive at Metropolis General, having heard that Tess was admitted. They discuss the reason for her being there and have a spat about the Blur, who Clark claims would side with him. They overhear a doctor (Dr. Coats) talking about Tess having a virus and go into her room to investigate. When Lois tries to question her, Tess wakes with her face horribly disfigured and she violently flings Lois across the room. Clark has to hold her down to be sedated.
At Watchtower, Chloe is working on her computer but quickly changes the display when Dr. Hamilton enters. However he has noticed and tells her they shouldn't have secrets from each other, but she says he's in the wrong business for that. Then Clark arrives with a sample of Tess's blood for them to analyze and identify the virus. Chloe hacks into security footage from the Luther Mansion showing the zombie-like intruders, and Dr. Hamilton hypothesizes that it may be a virus that affects the rage areas of the brain.
Clark speeds Dr. Hamilton across town to speak with the doctor at Metropolis General who reveals that the virus is probably airborne and the hospital is being quarantined, along with any other places Tess had been. They learn that she had been to the Planet, from where she was taken to the hospital. Clark realizes Lois is in danger from other infected staff at the Planet.
Clark speeds to the Daily Planet to save Lois and they fight off the horde but not before she is bitten. He gathers her up in his arms and carries her away to find someplace safe, and Lois smiles softly at this side of Clark she's never seen before.
At LuthorCorp, Oliver is with the female cop who had chased after him. He is getting drunk as she walks around in just her shirt. She finds a picture of Lois in his wallet and he appears pained to look at it. Oliver then downs some pills, claiming to have been "awake since Tuesday and those pills are the only thing keeping me vertical". The cop embraces him and knocks off his belt buckle, which they discover has a camera built in. After a brief spat when she accuses him of using the camera to put a sexy video on the internet, the cop leaves. Oliver decides that it was Tess who planted it to spy on him.
Meanwhile, Chloe has isolated a suspect enzyme from Tess's blood and Dr. Hamilton says the DCA think the virus was deliberately released by someone. He also states that the virus induces sleep, during which it germinates and takes over the infected person. Chloe says an antidote can be made if they can find a blood type which contains that enzyme. Upon looking at the data, Dr. Hamilton says he's only seen a blood type like that once and it belonged to Davis Bloome.
Clark and Lois are holed up in an office at the Planet while he wraps the wound on her leg. He tells her the infection is passed by an airborne virus, so she says they might not make it if they go outside. Saying she wouldn't want to go out without closure, she asks if he has any deep dark secrets. He dodges it by asking about hers and she tells him that she wanted to work with the Blur because she wants to be with him, saying she's never felt a connection like that before and doesn't want to be alone anymore. They gaze silently into each other's eyes for a few moments until Clark's phone rings, with a text message from Chloe to go to Watchtower. Suddenly, an infected person crashes through a glass door and Oliver follows with a 12 gauge pistol grip Remington 870 pump action shotgun which he has just fired. He says he was looking for Tess. They realize that sleeping induces the infection, so Clark leaves them boxed up in the elevator while he goes to get help, after specifically telling Oliver not to let Lois fall asleep.
Clark speeds to Watchtower and agrees to their plan to draw his blood using a needle dipped in liquid kryptonite. This proves extremely painful for Clark and renders him unconscious. Chloe and Dr. Hamilton have no choice but to leave him there so they can produce and deliver the antidote in the water supply.
Ollie and Lois are trying to stay awake as Lois comments about how far he has fallen, seeing him take pills to stay awake. Then Oliver catches sight of himself in a mirror and tells her to say he's full of it and that he misses her. But when he turns back to her, she has fallen asleep. He tries to wake her but the rage takes over and she leaps through the ceiling of the elevator.
Back at Watchtower, Clark awakes [exactly as he did at the beginning of the episode] to his phone going off.
Chloe and Dr. Hamilton are aboard the Queen Industry jet, having already released the antidote into the water supply and now ready to release it into the clouds so it will mix with the coming rain storm. Dr. Hamilton tells Chloe that he knows she has been tracking all the heroes, trying to protect them. She asks if he will keep her secret and he says she'll have to trust him.
At the Daily Planet, Lois attacks Clark, throwing him through a window into the street outside. He restrains her and tells her she will be ok, just as the rain begins to fall. She continues to struggle for a few moments before going limp, and soon wakes up normal. They embrace in the rain as other citizens of Metropolis fill the streets, also cured.
Clark finds Oliver drinking in an alley and yells at him for not being able to do something so simple as keeping Lois awake, asking if any part of the person he used to know is still there. Oliver admits that he looked in a mirror and Clark was right: he'd been running away from who he really is but now he knows. He thanks Clark, who leaves, and then pulls his Green Arrow suit out of a bag as he walks into the alley. He pours the remainder of his booze on it and sets it on fire.
At the farm, Clark is going through his wallet and finds an old picture of Lana. He puts it in an old photo album next to other photos of her. Lois enters and thanks him for helping her, saying she didn't remember being a zombie. But she did remember seeing a new side of Clark, which "starts with an 'H' and ends with an 'ero'." He jokes that he wasn't even wearing red and blue and she claims he has a long way to go before he can do that. She says they make a good team, but that he never did tell her his secret. As he tries to think of something to say, she says "Relax" and goes to punch his arm, but he instinctively grabs her arm and she smiles at him, telling him to save the mystery. She leaves, but just outside the door she momentarily has the same vision that has been haunting her dreams. She leaves quickly as Clark looks on concerned from inside the house.
The man who was the hospital doctor (Dr. Coats) who treated Tess enters an abandoned warehouse, and it becomes clear that he is one of Zod's soldiers. He is reprimanded by Major Zod for having released the virus because Zod fears it will break their cover. Coats says that, while it was a risk, it confirmed his suspicions that Jor-El survived and has taken the power from the yellow sun, and is using his powers to be a savior for humans. He presents Zod with the symbol for the House of El as proof. Zod asks if he was successful in finding this man, and Coats presents him with the vial of the blood used to create an antidote. Zod seems to congratulate him and tells him to kneel, but he then cuts off his head with a sword. He stands over the body, in the sunlight shining through a skylight in the ceiling.