collect. Cutscenes with occasional quick time events are featured at regular intervals to advance the story. As the player progresses throughout the game, a variety of computer-controlled monsters will try to hinder the player's progress. The player can acquire and use multiple weapons, including combat knives, firearms, and grenades. Some weapons can be customized with additional parts to improve their performance. A creature called Nemesis is the game's primary antagonist and pursues the player in key moments. He gradually mutates into more aggressive forms as the player defeats him during several encounters. The player has a certain amount of health which decreases when Jill or Carlos take damage. On higher difficulty settings, ammunition and health recovery items are scarce, and getting past opponents without killing them is generally encouraged. Jill has the ability to dodge incoming attacks at close range, while Carlos can perform melee attacks to stagger opponents. If Jill or Carlos die, the player must start the game again from the last save point. Once the player completes the game on the highest difficulty setting, two additional difficulty modes can be unlocked. These disable autosaves, make opponents tougher to defeat, change certain encounters, and rearrange item locations. Additionally, upon completing the game for the first time, an item shop is unlocked in the game's main menu, allowing the player to spend points on in-game advantages such as items that boost the player's healing and damage, as well as entirely new weapons. Points are earned by completing a number of challenges, ranging from finding all weapon upgrades to destroying hidden bobbleheads known as Charlie dolls. Unlocking items is essential to completing the game's most challenging difficulty modes. Plot On September 28, 1998, 24 hours prior to the events of Resident Evil 2, most of Raccoon City's citizens have mutated as the result of an outbreak caused by the T-virus, a mutagenic virus secretly developed by the pharmaceutical company Umbrella. Jill Valentine, former member of the Raccoon Police Department's Special Tactics And Rescue Service (S.T.A.R.S.), is attacked in her apartment by an intelligent bioweapon known as the Nemesis T-Type, programmed by Umbrella to silence surviving S.T.A.R.S. members. Briefly accompanied by fellow S.T.A.R.S. officer Brad Vickers before he is killed by zombies, Jill evades Nemesis and is then rescued by Umbrella Biohazard Countermeasure Service (U.B.C.S.) mercenary Carlos Oliveira. Carlos explains that he and his group of surviving U.B.C.S. mercenaries—Mikhail Victor, Tyrell