Leon B, known in Japan as Leon last part (レオン裏 Reon-ura ), is a story scenario in Resident Evil 2. It is unlocked upon completing the Claire A scenario. It differs from the Leon A scenario, in that the police car the two drive in the beginning hits the lamp post head-on, with Leon being forced by a tanker crash to head through the Raccoon City Police Station's helipad.
Unlike Claire A Scenario, it's actually a short trip through the streets. After being separated from Claire, Leon heads down the street into the Raccoon Police Station's parking lot, which leads him to the roof of the police department.
Raccoon Police Station
Shortly after his arrival, a helicopter flies in and drops something into the building. Leon goes inside to investigate, and is confronted by a gigantic humanoid monster, known as a T-00. Leon manages to evade this monster, but as he will soon discover, it is never far behind him. In an upstairs hallway, Leon stumbles upon a little girl, who immediately mistakes him for a zombie. Although Leon gives chase, she runs away and escapes. At that moment, Claire enters the room and inquires about the little girl, whom she had just followed. The two make plans to find the little girl, and then find a way out of the city. Leon gives Claire a radio so they can keep in contact.
Leon heads down to the parking garage to search for survivors, but is abruptly stopped by the sound of a gunshot. He turns to find a mysterious woman, whose name is Ada Wong. Ada tells Leon that she's trying to find a reporter named Ben Bertolucci, who has information regarding the outbreak. She believes him to be in the cell block, but a police truck is blocking the entrance. With Leon's help, they are able to move the truck and enter the cell block. After locating Ben, Ada explains that she is searching for her boyfriend, John Clemens, an Umbrella worker who disappeared 6 months earlier. Ben claims that he doesn't know anything, and refuses to leave his cell, saying that the zombies aren't the only things haunting the station. As if on cue, a hideous roar echoes through the cell block from somewhere nearby. Still refusing to leave his cell, Ben tells Leon and Ada to search for a way out through the sewers.
The two investigate the sewers, but quickly find themselves at a dead end. Noticing a small ventilation hole, Leon gives Ada a boost. On the other side of the wall, Ada finds the little girl Leon saw previously, who runs away again, this time dropping her pendant. Ada decides to carry the pendant for the girl until she's able to return it. After the rest of her search proves fruitless, Ada reports back to Leon, but because she can't reach the ventilation shaft on her own, she is forced to find another way back. Leon then receives a call from Claire, who has apparently found the little girl.
While backtracking through the cell block, he suddenly hears Ben crying out for help, just before being struck down by an unknown monster. Leon finds Ben, critically wounded, who tells him the truth about Chief Brian Irons' involvement with Umbrella in covering up the Mansion incident, before succumbing to his injuries. Ada then arrives to inform Leon that she is heading to the Chemical Plant. After she departs, Leon receives another message from Claire, explaining that she's heading to the sewers and getting out of the city. Fearing for her safety, Leon races through the sewers, only to be confronted by the same monster that attacked Ben. After a brief skirmish, Leon manages to severely wound the monster, which then topples out of sight over a railing.
Eventually, Leon catches up with Ada, and convinces her that they must work together in order to get out alive. Passing deeper into the sewers, they spot a mysterious woman who runs away from them, but Ada chases after her. The woman draws her gun and tries to shoot Ada, but Leon jumps in to save her, taking the bullet himself. With Leon unconscious, Ada pursues and confronts the woman, whose name is Annette Birkin, a scientist affiliated with Umbrella. Recognizing Ada as John's girlfriend, Annette reveals that John is a zombie, and that the creature in the police department is her husband, William Birkin, who caused the city outbreak to protect his experiment, the G-Virus. Annette then notices the pendant that Ada is wearing; the same pendant she had given to her daughter, Sherry Birkin. Ada explains that she was merely holding on to it for the girl, but Annette does not believe her and demands that she hand it over. A brief struggle ensues, which ends with Ada knocking Annette into the sewage below. Wondering why the pendant is so important to Annette, Ada opens it and discovers a sample of the G-Virus hidden within.
At this point, Leon regains consciousness and begins to search for Ada. After reuniting with her in the garbage disposal area, Ada treats and bandages his bullet wound, and the two continue on their way through the sewers.
Umbrella's Underground Lab
Leon and Ada find the platform that leads down to Umbrella's underground lab. However, the platform was already taken down by Claire. Leon finds the key to the platform in the control room, but is once again attacked by the T-00. After eluding the monster, Leon and Ada use the platform to descend to the lab, but are ambushed by the mutated William, who knocks Ada out of commission. Leon heads outside to find William, who has mutated into a much more menacing form. He defeats William, but unfortunately, the platform stalls due to overheating. With Ada lying wounded, Leon exits the platform car and accesses a panel which leads to the basement of the lab. Suddenly, he hears the platform restart and continue its descent to the lab. Working his way up to the surface, he enters the platform car, only to find that Ada has vanished.
Leon heads back down to the basement and is confronted by Annette. She accuses Leon of killing William, and tells him that she created another G-Virus to fulfill William's legacy. She also tells Leon that Ada is a spy, working for a secret organization that seeks to obtain the G-Virus, and that she only posed as John's girlfriend to get information about Umbrella. Leon does not believe her, however, and Annette is about to shoot him when she is interrupted by the T-00. While Annette uses the distraction to escape, the monster stalks Leon into the power room and eventually corners him. As the T-00 closes in on Leon, a sudden burst of gunfire diverts its attention, and it turns to regard its new target, Ada. Though she succeeds in drawing the monster away from Leon, her bullets have little effect upon it, as it swiftly closes in and hoists her into the air. In response, Ada fires her gun directly into its face, causing it to throw her violently into the self-destruct control panel, before falling over the railing and into the blast furnace.
Leon tries to tend to Ada, but she is gravely wounded. In her final breaths, she confesses her love for Leon and encourages him to go on without her. She then kisses Leon, before apparently dying in his arms. Although sickened with rage over her loss, Leon has no time to mourn, as the lab's self-destruct sequence has been initiated.
Upon exiting the power room, Leon receives another message from Claire, imploring him to pick up Sherry in the security office while she finds a vaccine for her. Leon heads to the security office and takes Sherry to the underground train. With no power being supplied to the train, Leon leaves Sherry behind to find a power source, but is unexpectedly attacked by the T-00, who emerges from the blast furnace as an even more horrifying creature. Leon tries his best to destroy it, but his gunfire seems to have no effect on it.
Suddenly, a familiar voice calls out to him, and a mysterious woman, whom Leon identifies as Ada, tosses him a rocket launcher. Leon destroys the monster with the rocket launcher and heads back to the train, having succeeded in restoring power. As it begins to pull away from the platform, Claire appears and is barely able to make it aboard the train. By the time she arrives, Sherry is unconsicous, but Claire administers the vaccine and cures her of the G-virus. As the train races through the tunnel toward safety, a great explosion is heard as the lab is destroyed behind them.
"It's over", Leon declares. While Claire knows that her search for Chris must continue, Leon heads to the control panel, where he says his final goodbye to Ada.
The Last Escape
Despite having escaped the Umbrella laboratory, they quickly learn that their nightmare is far from over, as a sudden tremor rattles the train. When Leon goes outside to investigate, he discovers that the train has initiated a self-destruct sequence due to a biohazardous creature that has somehow made its way onto the train. Even worse, he finds that the system has automatically sealed all of the doors, leaving him to face William Birkin in his largest, most grotesque form.
Unable to hold William off for long, Leon tells Claire to stop the train, but the door to the control panel is still locked. Using her small size to her advantage, Sherry manages to reach the control panel room through a small passage, while Claire climbs underneath the train to save herself from William. Meanwhile, Leon, who has escaped to the roof of the train, is slowly working his way towards the control room. When he opens the roof hatch, he finds Sherry and directs her to press the emergency stop button. She does, and the train finally screeches to a halt. Leon, Claire, and Sherry see the end of the tunnel and head towards it as fast they can, leaving William trapped on the train, which then explodes into an enormous ball of fire.
As Claire and Sherry try to catch their breath, a restless Leon urges them onward, explaining, "Hey, it's up to us to take out Umbrella."
- Depending on how Claire defeated the Alligator, if she just defeats the Alligator without using the gas cylinder, it'll appear again in Leon's story for Leon to defeat once more. If she defeats the Alligator using the gas cylinder, blowing its head off, the Alligator won't appear in Leon's story, and Leon will just simply meet up with Ada.
- If the player defeated the Alligator as Claire using the gas cylinder, it remains defeated in Leon's B scenario. However, Ada will still remark "That's two I owe you," when reuniting with Leon, despite the Alligator never making an appearance in this case.
- Although Chief Irons and Annette both die in Claire A, Chief Irons' body will be present in Leon B, but Annette's will have seemingly disappeared by then.