The player can use a variety of firearms to defeat enemies, ranging from pistols to a rocket launcher. Aside from enemies, parts of the environment, such as explosive barrels, can be shot at, causing them to explode and damage nearby enemies. The game also introduces the ability for players to dodge attacks or perform a quick 180-degree turn to evade enemies. The player has a certain amount of health which decreases when attacked by enemies. Health is regained with first aid sprays, as well as herbs, which can be used separately or mixed together to increase their healing effect. The game also features an ammunition creation system that allows players to create new ammunition from different varieties of gunpowder. In addition to engaging in combat, the player must often solve puzzles that focus on logical and conceptual challenges.
During certain situations the player will be put in a perilous situation, where they will be prompted to choose between two possible actions or suffer a certain penalty, if not instant death. These choices affect how the story unfolds and which ending is achieved. Additionally, a creature called Nemesis is encountered multiple times throughout the game as a recurring boss. Nemesis is considerably more powerful than the player and has the ability to use a rocket launcher as a weapon, dodge incoming fire, and pursue the player from one area to the next. During one of these encounters, the player can choose to either fight Nemesis or run until he is evaded. A variety of encounters are possible, with some being mandatory, and some varying in nature and location based on certain choices made by the player. Even if evaded or defeated during one of these encounters, Nemesis will inevitably continue to pursue the player until the end of the game.
Upon completing the main story mode, a minigame titled "The Mercenaries: Operation Mad Jackal" is unlocked. In Mad Jackal, the player must control one of three members of the Umbrella Biohazard Countermeasure Service that Jill encounters during the main game and run from one side of the city to the other within a limited amount of time and resources. However, the starting time limit given is insufficient to actually perform this task directly, and the player must continuously receive time extensions by performing certain actions such as defeating enemies, rescuing civilians and exploring hidden areas. Depending on rank received and difficulty chosen, completing the main game may unlock alternate costumes for Jill and epilogue files that detail the activities of different characters following the events of the game. The mercenaries minigame and alternate costumes for Jill are available from the start of the game in the Microsoft Windows and Dreamcast versions of the game.
Plot
On September 28, 1998, 24 hours prior to the events of Resident Evil 2, former Special Tactics And Rescue Service (S.T.A.R.S.) member Jill Valentine attempts to escape from Raccoon City. Most of the population has been transformed into zombies by an outbreak of the T-virus, a new type of biological weapon secretly developed by the pharmaceutical company Umbrella. On her way to the Raccoon City Police Department, Jill runs into fellow team member Brad Vickers, who is killed by a new enemy. This creature, Nemesis, is a bio-organic weapon programmed to target surviving S.T.A.R.S. members, witnesses of Umbrella's experiments. As she evades Nemesis, Jill encounters three surviving members of the Umbrella Biohazard Countermeasure Service (U.B.C.S.): Carlos Oliveira, Mikhail Victor and Nikolai Zinoviev. Nikolai explains to Jill and Carlos that a rescue helicopter can be contacted if they manage to reach the city's Clock Tower and ring the bell.
As they make their way to the tower, Nikolai disappears and is presumed dead, while Nemesis corners the remaining members of the group on the cable car headed to the tower. Mikhail sacrifices himself with a grenade, causing the car to crash into the tower's main courtyard and separating Jill and Carlos briefly. At the Clock Tower, Jill summons the helicopter by ringing the Clock Tower's bell before being confronted by Nemesis, which destroys the helicopter and infects Jill with the T-virus. Jill manages to temporarily defeat Nemesis but falls unconscious due to the T-Virus. Carlos finds Jill and takes her to safety within the Clock Tower. Three days later, he manages to find a cure for Jill's T-Virus infection in the Raccoon City General Hospital. He returns to Jill and injects her with a vaccine, saving her.
After she regains consciousness, Jill proceeds towards the Raccoon Park and enters the park caretaker's cabin. There, she runs into Nikolai, who is alive. Nikolai is revealed to be one of the "supervisors" sent into Raccoon City to gather combat data of Umbrella's bio-weapons. Nikolai retreats, and Jill is confronted by a massive worm-like creature. Jill defeats the creature and escapes to an abandoned factory at the rear of the park. Inside the factory, Jill meets up with Carlos, who tells her that the US government is planning to launch a nuclear missile into Raccoon City to eradicate the T-Virus infestation. After confronting Nemesis and grabbing a keycard needed to escape, Jill learns from the factory's control tower that the missile attack on Raccoon City has begun, with only a short time left before the city is destroyed.
