A city on the coast of the United Kingdom suffers a bioterrorist attack from B.O.W.s that have never been seen before. The BSAA tracks the source of the attack to a cargo ship and sends Jane Bradstreet and Scarlet Knight to the vessel to investigate. When the agents board the ship, it begins to move. They encounter the same bioweapons that attacked the city, alerting the crew of their presence. Eventually, the BSAA agents find the pilot of the ship, who had turned into a Draugr himself. After they kill him, Scarlet is able to find the coordinates of the ship's destination, which is an uninhabited tropical island. When nearing its destination, the cargo ship is attacked by the Lyngbakr, causing it to sink. With debris in the way, Jane and Scarlet attempt to escape while holding off the bioweapon. Just before the ship arrives at the island, Jane and Scarlet seemingly kill the Lyngbakr with their weapons, as it ceases activity.
The agents swim to land and begin scouting the island. Roaming among the forest are more bioweapons, including some of which had yet to be encountered. The BSAA agents are able to find the facility producing the bioweapons, named Jötunheimr, but they get separated when they are ambushed by a swarm of Wargs. Scarlet, who is farther away from the facility, urges Jane to go on without her. With no other option, Jane complies and enters the building. Sneaking through the facility, she soon comes across an unoccupied security room and finds Dom Lee in a cell. Disgusted that a civilian is being experimented on, Jane decides that rescuing Dom is another priority. Once she figures out exactly where Dom is being held, she immediately goes to his cell, kills the nearby guards, and frees the prisoner. Jane briefly introduces herself, prompting Dom to do the same and explain that Charles Burr, the head researcher of the facility, had been using the virus in his blood to develop bioweapons.
Three months prior to the previous events,
Dom and a friend, Maurice Johnson, are working at the fifth floor of a building in the city of Tatamy. A t-virus outbreak erupts in Tatamy, causing the people of the first few floors to be infected. The infection soon spreads to the fifth floor itself. Dom and Maurice are lucky enough to find two firearms. Unfortunately, all of the building’s elevators fail to work. Due to the layout of the building, there are multiple staircases that lead to the base floor, allowing the two to strategically plan their escape. Once Dom and Maurice reach the first floor, a hunter ambushes the survivors and impales Maurice with its claws, killing him. Dom avenges Maurice shortly afterwards and then fights his way out of the building.
Once outside, Johnny Lee, Dom's adoptive uncle, arrives in his car. After he splatters their way through a good portion of the city, the vehicle runs over a series of stray zombies at a bad angle, and flips over. Both Johnny and Dom are forced to get out and make their last stand. All nearby zombies are eventually eradicated, but Johnny’s heroism sustains him multiple bite wounds. As he begins succumbing to infection, Johnny tells Dom that the latter is immune to the t-virus, because he naturally possesses another virus within himself – the Hyper-evolutionary virus (HEV) – which eliminates all degrading mutations but keeps positive ones. Before Johnny can fall unconscious, he asks Dom to put him out of his misery, and hands his nephew his rifle. Reluctant, Dom accepts the rifle and shoots his uncle in the forehead. Shortly after Johnny's death, multiple hunters surround Dom.
Back to the present time, the whole facility is alerted of Dom's rescue. To prevent their escape, Burr locks down all doors of the building and releases his bioweapons after Dom and Jane. When a handful of lesser bioweapons proves to be unsuccessful, Burr starts to unleash his more powerful creatures, ignoring the fact that doing so is overkill for a mere pair of humans. Regardless, Dom and Jane are able to find weapons strong enough to eliminate these monstrosities, narrowly surviving each encounter. Having no way of leaving the facility, due to the building's doors being locked down, Jane and Dom decide to confront Burr directly. On their way to the control room, they catch a glimpse of an unknown entity who appears to not work for Burr.
The unknown entity Dom and Jane had seen earlier breaks into the control room and shoots all of its occupants, including Burr. The entity then steals a sample of HEV, but Burr injects himself with a special HEV strain he had in his pocket, mutating into a special kind of Draugr, and then tries to stops the thief. His effort is futile, however, and the unknown being escapes. Burr began eating the corpses of his subordinates, using their biomass to mutate even further. Upon entering the control room, Dom and Jane find that Burr had transformed into a centaur-like creature. Not as powerful as his better creations, Burr is inevitably defeated in his struggle to finish off Jane and Dom. While the collapsed Burr is still alive and conscious, Dom mercilessly ignites him with a flamethrower, inducing an agonizing death. Jane then runs to the controls of the building, only to find out that the doors had already been opened. On their way out, Dom and Jane face Burr's ultimate bioweapon – Surtr. Throwing everything they have at the massive bioweapon, Dom and Jane eventually bring it down. Jane tells Dom to follow her to the island's port, hoping that there would be ships remaining.
Even outdoors, bioweapons continue to chase after Jane and Dom, who soon meet up with the injured Scarlet. Before the three can reach the ship, a Hræsvelgr drags Scarlet away with its tongue. Scarlet tells Jane and Dom to leave her, as she no longer has any chance to escape. To not let Scarlet's sacrifice be in vain, Jane and Dom agree to her request and escape onto the vessel while Scarlet continues to maintain her last stand until she is overwhelmed and eaten by a swarm of Wargs. On their way off the island, the Lyngbakr attacks once more. With this ship sinking like the last, Jane and Dom board a lifeboat. Now better-equipped, the two of them put down the mutated shark for good. BSAA helicopters arrive a few hours later to extract Jane and Dom, and the latter is then taken into BSAA custody.
While piloting a jet, the unknown entity who infiltrated Jötunheimr is speaking to Albert Wesker, telling the megalomaniac that he had obtained a sample of HEV. Wesker reveals the person's name to be Tony Wesker, who is his fraternal twin brother.
The gameplay of RE:HE is very similar to that of RE5, especially the active gameplay. Just like RE5, the player is dependent on the second player or AI, where many parts of the game require the partner for assistance, such as pulling switches, freeing each other, and reaching otherwise-unreachable platforms. Unlike RE5, however, the partner, and sometimes the main character, changes several times as the story progresses. When the player's health drops to 0, he/she will enter a DYING state, which functions exactly the same as it did in RE5; one character must rescue the other. The melee system and the damage scale is also identical to that of RE5. RE:HE also features its own Mercenaries minigame.
In singleplayer, the partner AI has been improved. The partner AI generally makes "smarter" decisions and is also more skilled at using weapons. If the player performs an arm-shot-triggered melee attack, the AI partner, if nearby, will almost always initiate his/her own arm-shot-triggered melee attack in order to set the player up for a combo finisher.
Also much unlike RE5, the game does not feature a merchant/store where the player can purchase and upgrade weapons. All non-character-exclusive weapons within the game must be found in order to be usable. The majority of the firearms in the game also do not feature a laser sight for aiming; in place of the laser is a simple, faint crosshair.
The inventory system of RE:HE, although similar, also works differently from that of RE5. A character's inventory features two slots for "primary weapons," two slots for "sidearms," and five additional slots for additional items. Due to the nature of the story, there is no storage system in the game that can be accessed, and the player can only keep whatever weapons he/she ends up with by the end of the level. Because of this, some weapons can be encountered multiple times throughout the story. As in RE5, the player can manually equip the AI partner character before each chapter.
Another notable difference, albeit minor, is in regards to knives. While every character has a knife in RE5, some characters in RE:HE do not. These characters, instead, can melee nearby enemies at any time, but deal only 30 damage and briefly stun their targets.
Resident Evil: Hyper-Evolution has three difficulty modes: Normal, Veteran, and Professional. Compared to Normal difficulty, on Veteran difficulty, ammunition is less common, and enemies deal noticeably more damage, are more durable, and appear in greater numbers. Veteran difficulty can also be considered the "canon" difficulty. On Professional difficulty, many enemies have dramatically more health than they do on Veteran difficulty, but nothing else changes.
RE:HE takes a more realistic approach on weapons in terms of damage and how they function in real life when compared to other Resident Evil titles. Because of this, several "rules" to weapon stats are included in the game.
Reloading and Capacity
Most weapons will have a different capacity depending on when they are reloaded. These weapons will have one extra bullet if reloaded mid-magazine, but will not have that extra bullet if reloaded before being empty. This is because in many firearms, a shot is loaded into the chamber of the weapon right after the previous shot, unless there is no shot left to be loaded.
Many weapons also reload somewhat more slowly if reloaded after being empty, due to the weapon being needed to be cocked.