Picking up six years after Resident Evil 2, the fourth game in the series follows a former cop (now US agent), Leon S. Kennedy, to Europe on a top-secret mission to investigate the disappearance of the president's daughter Ashley. As Leon encounters unimaginable horrors, he must find out who or what is behind everything. Old friends...and enemies...lurk around every corner as Leon attempts to find out who is truly behind the kidnapping of the president's daughter.
Resident Evil 4 introduces a new camera system and gameplay mechanics, allowing for more fluid movement and aiming. The game features a new AI system and open environments where enemies can work together, making for a more intense experience. Enemies are now humans, which allows them to interact with the environment in new ways.
The item system has been revamped, allowing for more space to hold items and weapons. Leon can collect treasure from enemies or the surrounding area and visit the "merchant" to purchase upgrades and powerful weapons. The game also features a Mercenaries mode, where players can play survival scenarios as characters like Hunk and Albert Wesker.
Later released platforms come with an additional story mode called Separate Ways , which unlocks after completing the main game. This story follows Ada Wong and provides insight into her actions during the main campaign.