|01 "Pilot"||09 "Harvey Dent"||17 "Red Hood"|
|02 "Selina Kyle"||10 "Lovecraft"||18 "Everyone Has a Cobblepot"|
|03 "The Balloonman"||11 "Rogues' Gallery"||19 "Beasts of Prey"|
|04 "Arkham"||12 "What The Little Bird Told Him"||20 "Under the Knife"|
|05 "Viper"||13 "Welcome Back, Jim Gordon"||21 "The Anvil or the Hammer"|
|06 "Spirit of the Goat"||14 "The Fearsome Dr. Crane"||22 "All Happy Families Are Alike"|
|07 "Penguin's Umbrella"||15 "The Scarecrow"|
|08 "The Mask"||16 "The Blind Fortune Teller"|
- "Drugs that worked on an epigentic level. Imagine an army made up of soldiers so strong that they can tear a man apart with their bare hands."
- —Professor Isaac Steiner to Detectives Gordon and Bullock
Gordon and Bullock search for The Source of a new street drug that causes euphoria then death. Meanwhile, Oswald Cobblepot works his way deeper into Maroni’s inner circle and Fish Mooney continues to plot against Falcone.
Bruce continues his thorough investigation of the Arkham project, explaining to Alfred that he is trying to find out how both the Maroni and Falcone crime families managed to get a stake in Arkham without anyone at Wayne Enterprises doing anything to stop them.
At Bamonte's, Maroni is still furious about the robbery of the restaurant, and orders Frankie to organize a robbery of Falcone's casino, while the restaurant's new manager, Oswald Cobblepot, listens in on every detail.
Elsewhere in Gotham, a man with a disfigured ear hands a street guitarist a small glass vial with a green substance inside. Seeing the words "breathe me" on the bottle, the guitarist shrugs and inhales it. Moments later the musician breaks into a convenience store and starts guzzling milk off the shelves. The owner tells him to stop, but the guitarist throws him back with a burst of inhuman strength.
Close by, Detectives Gordon and Bullock are in the middle of lunch, when they hear the sound of the alarm. Jim runs to the store, while Bullock protests that they are off-duty, but follows half-heartedly. Gordon interviews the store owner, badly injured, who reports that the attacker started going crazy, before pulling the store's ATM machine out of the wall and taking off with it. Bullock tries to cut the interview short, saying they are homicide detectives, and this is not their problem, since no one was killed. Gordon asks the owner to describe the attacker's vehicle, and the owner says that is just it, there wasn't one - the man ripped the ATM out of the wall with his bare hands. Gordon and Bullock trade a look, realizing that something unusual and dangerous is going on.
At a warehouse, Carmine Falcone meets a gathering of his capos, including Fish. Falcone begins by assuring them that their partial share in the Arkham development project is not a loss, they will all profit from it and a crime war was averted. Falcone's Russian subordinate, Nikolai disagrees, saying that Maroni will be emboldened by his success and the Falcones should strike back first. This leads to an argument between Nikolai and Fish, with Nikolai throwing in a few comments about a woman's "proper" place among men in his country. Falcone cuts in, reminding them that they are family.
Gordon and Bullock began to explore Gotham in search of information about the drug addict musician. A photo copied from the store's security camera is recognized by a prostitute named Charmagne, who names the man as Benny and directs them to his usual hangout. The two detectives find him under a bridge, amid piles of empty milk bottles. Benny is convulsing and pleading for help, saying the drug that the man with the disfigured ear gave him felt wonderful at first, but now it's doing something bad to him. Gordon says they can help him, but Benny throws them back with another burst of strength, then lifts the ATM machine over his head, preparing to throw it at them - before his skin turns pale and his face becomes disfigured and out of shape, and he collapses, dropping the ATM on himself. Gordon worries aloud what might happen if there is any more of this mystery drug in Gotham. Later that night, the same man hands out more vials of the drug throughout the city.
At Wayne Manor, Bruce delves further into his family's business, deciding to attend a charity event organized by the company and interact with members of the board.
The next day both the streets of Gotham and the GCPD are overrun by people under the influence of the drug, dubbed "Viper". After running tests on the drug, Edward Nygma, totally fascinated by the situation, reports to the detectives and Captain Essen that the drug fuels the subject's super-strength by consuming the body's calcium at a hyperactive rate - hence the subject's need to replenish calcium by drinking milk. The problem is, the consumption is too rapid, and eventually the subject's bones crumble and they die of suffocation. Essen asks why anyone would be giving away samples of such a dangerous substance, and Gordon theorizes that they are creating a demand and plan to eventually sell the drug on the streets. Essen finds it hard to believe that anyone would pay money for a drug that kills 100% of its users, but Bullock says that before it kills them, it makes them feel wonderful and gives them super-strength, so some junkies in Gotham will be desperate enough to take it.
Gordon asks Nigma how the drug is manufactured, and Nigma says that the process is incredibly sophisticated, and only someone with access to a state-of-the-art lab could do it. Gordon then asks who has the best-equipped lab in the city, and Nigma responds, WellZyn, a pharmaceutical subsidiary of Wayne Enterprises. They are interrupted when Charmagne, the drug's latest victim, goes berserk before she can be put into the holding cells, throwing several officers around the room before the final effects take hold, and she collapses in a shapeless heap, dead.
At Bamonte's, Maroni and Frankie are still arguing, with Frankie saying that Falcone's casino is too well-guarded, and robbing it will cost them too many men. Determined to show his worth, Oswald approaches the table and says he knows a janitor who worked at the casino, who would know about the building's access tunnels. Maroni asks him how he knows this, and Oswald admits that he used to work for Fish Mooney. Maroni laughs, saying that makes for a funny story - before slamming Oswald's head down onto the table.
At the GCPD, Gordon and Bullock receive a visit from Taylor Reece, an attorney for WellZyn, who assures them that WellZyn has no connection to the manufacture of Viper, and that legal action will be taken against anyone who claims as much, but she is there to help them. Gordon gives her Benny's description of the man with the disfigured ear, and she identifies the man as Stan Potolsky, a biochemist formerly employed at WellZyn who became unhappy with his work and tried to cut off his own ear in protest, before he quit.
While Harvey leaves to get an arrest warrant for Potolsky, Jim receives a visit from Frankie Carbone, who asks Gordon to meet with Don Maroni. Gordon tries to refuse, but Frankie asks if the name Oswald Cobblepot means anything to him. Gordon freezes.
Arriving at Bamonte's, Gordon is greeted by Maroni, with a battered Cobblepot sitting at his right hand. Maroni asks Gordon to tell him the exact same story that Cobblepot did, and if their stories match, then Cobblepot is telling the truth; if they do not, then one of them is lying and Maroni will kill both of them. Gordon, unable to know exactly what Cobblepot told Maroni, decides to go with the truth: that he was investigating the murder of the Wayne family, and was used as a pawn in a conspiracy between the GCPD and Falcone to frame Mario Pepper for the murders; that to ensure his silence, Falcone ordered him to kill Cobblepot, but Gordon did not. Maroni absorbs that, then asks whether anyone - the GCPD, Mooney, or the Major Crimes Unit Detectives Cobblepot snitched to - knows he is still alive. Gordon wryly responds that if anyone did, they'd both be dead already. Maroni is delighted: not only is Cobblepot telling the truth, but his very existence gives Maroni a "brand-new weapon" against Falcone. Maroni thanks Gordon for his candor, and sends him on his way, warning him to keep his mouth shut.
Back at GCPD, Bullock dumps out a box of Potolsky's possessions, saying the man is a classic loner - no family, no friends, and no one he's really close to. Gordon looks through the box and sees a photograph of Potolsky with an old college professor of his.
The detectives interview Professor Isaac Steiner at Gotham University, who explains that Potolsky, while a biochemist by training, always had a deep interest in philosophy, and often came to Steiner when he felt morally conflicted about his work. Bullock is confused - Reece told them that Potolsky made shampoo and other domestic products, what's morally troubling about that? Steiner gives a bark of laughter and says WellZyn lied to them: Potalsky was actually put to work on biological warfare research - specifically, designing epigenetic drugs that could create "super-soldiers." Gordon mentions Viper's nasty side-effects, and Steiner responds that Viper was just the first test strain, and WellZyn eventually succeeded in creating a non-lethal version, called Venom. Steiner then explains that Potolsky pleaded with his bosses to stop the research, but when they refused, he went directly to Thomas Wayne. Wayne apparently succeeded in shutting the project down, but after his death, it was immediately reinstated, and Potolsky quit in disgust.
Gordon notes that Steiner doesn't seem particularly upset at learning of the destruction Potolsky is causing, and quickly deduces that he and Steiner are working together. Steiner congratulates Gordon on asking the right question, then grabs a vial of Viper from the candy dish on his desk and inhales it. Gordon is forced to shoot down the old man as he is about to kill Bullock. Before Steiner dies, Gordon demands to know what Potolsky's next target is, and the professor wheezes that Potolosky is going to strike back against Wayne Enterpises, and their empty "altruism" will not erase their crimes. Gordon realizes that Potolsky plans to target Wayne Enterprises' charity event that afternoon.
Disguised as a waiter, Stan Potolosky sneaks into the hotel with a full tank of Viper, and then goes to the roof to connect it to the ventilation system.
Alfred escorts Bruce to the party, and he is introduced to Molly Mathis, a member of Wayne Enterprises' board of directors. Bruce wants to discuss the irregularities he found in the Arkham project, but they are interrupted when Potolsky appears on the television screens, saying he produced Viper while he was employed at WellZyn, and Wayne Enterprises is ultimately responsible for the suffering the drug has created. Bruce turns to Mathis and asks if this is true, and she replies, absolutely not.
Simultaneously, Gordon and Bullock arrive and tell everyone to evacuate the building. Thanks to their warning, the ballroom empties before the Viper arrives through the air ducts.
Gordon goes to the roof to confront Potolsky. He says his work is done, and WellZyn has been exposed, but if Gordon wants further proof, he should look inside "Warehouse 39." With that, he throws himself off the ledge of the roof and falls to his death.
Later, Gordon and Bullock visit the Warehouse, but are surprised to find an empty lab inside. Outside, Molly Mathis watches them from the backseat of a limousine, while confirming to someone at the other end of her cell phone that the warehouse was cleared before the detectives arrived, and they will find nothing.
At Wayne Manor, Alfred decides to help Bruce with his investigation. At first, he thought Bruce was chasing shadows, but the chaos at the party has made him wonder if there is really corruption within Wayne Enterprises, and whether that corruption had something to do with the Waynes' deaths.
Outside of Falcone's casino, Maroni, Cobblepot, and Frankie sit in a car, driving away after Maroni's men run outside with bags of stolen money. Maroni is delighted and congratulates Cobblepot for his role in their success.
Elsewhere, Fish and Nikolai share a night of passion while reviewing their plan to bring down Falcone.
Falcone, while feeding pigeons in a park, is enraptured when Liza walks past, humming the same aria that his mother used to sing to him as a child. Feigning surprise, she sits beside him and hands him one of her ear buds so they can listen to it together.
- The aria that Fish trains Liza to sing is "O mio babbino caro" (Italian, "Oh My Beloved Father"), from the opera Gianni Schicchi by Giacomo Puccini.
- Viper is mentioned to be a prototype of Venom.