Leon Chapter 4 is a chapter of Leon Story in Resident Evil 6. Leon and Helena arrive in Lanshiang and, running into Jake, Sherry, Chris and Piers, discover Simmons's whereabouts and meet the leader of Neo Umbrella, Carla Radames — whom they believe is Ada Wong, making Leon torn about what to do.
On board a plane heading to Langshiang, Leon and Helena talk about turning her in to clear his name. Leon states that it wouldn't have stopped Simmons. At that moment, the plane shakes; the two of them head to check on the pilot, finding a dead agent from The Family and cocoon where the pilot should be. It hatches into a Lepotica, which flees into the ceiling once damaged enough. Leon and Helena find the auto-pilot is on, and that there is trouble in the cargo hold.
Once in the cargo hold, they correct the pressure, but this forces the Leoptica out of the ceiling. It starts leaking gas, so Leon opens the cargo door, letting the monster fall to its doom. However, it turns out they were too late as the gas leaked to the passengers before they could get it out; leaving Helena to fight off the zombies, Leon pilts the plane for a landing. Crashing, Leon briefly catches sight of Ada.
Leon and Helena manage to survive the crash, getting off the plane. To Leon's surprise, he is reunited with fellow Raccoon City Incident-survivor Sherry Birkin. Now a federal agent, her current assignment is to protect Jake, the young man with her. It turns out, however, that Sherry's superior is none other than Simmons. Taken aback by Simmons' actions, Sherry reveals his location to Leon. Their meeting is interrupted by Ustanak, sent to take Jake back to Neo-Umbrella for his blood; however, he is crushed by a falling metal structure. Despite being separated in the ensuing fight, Leon promises to meet up with her again at Simmons' location.
On their way there, Leon and Helena catch sight of Ada, and attempt to get information out of her. However, at that very moment Chris of the BSAA shows up and, in a rage, accuses Ada of being the mastermind behind the attacks. Leon interjects, insisting that the real culprit is Simmons; as their argument reaches a boiling point guns are drawn, giving Ada an opportunity to escape. After convincing Chris that the both want justice, Leon lets the BSAA handle Ada, while he and Helena head after Simmons.
The two agents arrive to face off with Simmons just ahead of Sherry and Jake. Determined to settle this very personal vendetta themselves, Leon and Helena make cover for the younger pair to escape, then proceed to attack. However, Simmons is injected with the Enhanced C-Virus by a J'avo sent by Neo-Umbrella; fighting off the infection, Simmons falls onto a passing train. Leon and Helena jump on after him. Simmons listens to Ada telling him that he is being given a taste of his own medicine, in the hopes that it makes him the monster he always was; he crushes his phone in anger. Leon and Helena confront him, learning he killed Benford to keep the global political order from falling apart.
Giving in to his anger towards Ada for infecting him, Simmons mutates in a cetuar-like monster, and then a monstrous canine. The Family's helicopter follows the train through the battle, but ultimately leaves Simmons behind once its been decided that there is no hope of him being returned to normal. Simmons falls off the train, getting shredded by the wheels. Leon and Helena jump off, swimming to Tatchi on the other side of the tracks. Seeing the The Family looking for Simmons' remains, Leon decides they did what they could.
Just as the two agents begin to breathe a sigh of relief, they receive a transmission from Chris telling them to immediately escape the city. Looking to the sky reveals that it is already too late, as a missile explodes overhead,releasing gas that engulfs the city. It seems to the agents as if all hope is lost, as a tragedy greater than even Raccoon City or Tall Oaks unfolds before their eyes.
- Leon: (To Helena about the mutated pilot) You don't suppose that thing can fly a plane, do you?
- Helena: You fought this thing before and are still breathing? I'm impressed.
- Jake: You kidding? I get a kick out of this.
- Helena: You're not entirely sane, are you?
- Insert walkthrough here