Myst IV: Revelation is an adventure game in which the player experiences gameplay from the eyes of an unnamed protagonist referred to as the Stranger. Players explore interactive worlds known as Ages by using the mouse or keyboard, solving puzzles and uncovering the game's narrative. Players cannot move freely across each Age; instead, as in the previous games in the Myst series, they travel by clicking set locations called "nodes", where players can rotate their view in any direction. Revelation also features a "Zip" mode, which allows a method of rapidly crossing explored areas by skipping intermediate nodes; areas that can be instantly traveled to are stored as thumbnail representations for rapid movement across Ages.
The mouse cursor helps to provide visual cues for player actions and movement. The cursor appears as a hand that changes depending on what the player is hovering the cursor over. For example, to move in a direction, the cursor changes to point in the intended direction. If players can view an item in greater detail, the cursor changes to a hand holding a magnifying glass. By clicking and dragging the cursor, the player performs actions such as pushing, pulling, and tapping items.
Revelation features several gameplay enhancements that aid puzzle solving and plot progression. Early in the game, players receive a camera, which can be used to take screenshots or pictures of clues. Players can use an on-screen journal to jot down notes instead of having to write down clues as with previous Myst games. Much of the game's story is revealed via flashbacks triggered by an amulet that has the power to relay memories attached to objects. Zip mode, the amulet, the camera, and the journal are available via a menu on the bottom of the game screen.
Atrus calls the Stranger to his home in Tomahna to request his friend's assistance. Atrus is the writer of special books, which serve as links to worlds known as Ages. Twenty years earlier, his two sons, Sirrus and Achenar, destroyed his library on Myst and trapped their parents in order to plunder the wealth of Atrus' Ages. The Stranger's intervention saved Atrus, who had imprisoned his sons via traps intended for thieves. Atrus' wife Catherine hopes that, after twenty years, they have finally repented for their crimes. Atrus is not as sure his sons have reformed, and so wishes the Stranger to act as an impartial judge. After being knocked unconscious by an explosion, the Stranger realizes that Yeesha, Atrus' daughter, has disappeared.
The Stranger sets out to find Yeesha, travelling to the prison Ages of Spire and Haven. On Spire, Sirrus has used his scientific knowledge to craft explosives, allowing him to breach the chamber that contained the linking book back to Tomahna, and has escaped; journeying to Haven reveals that Sirrus has also freed Achenar. The Stranger journeys to the Age of Serenia and encounters Achenar, holding a "Life Stone"; Achenar tells the Stranger that Sirrus is mad and has captured Yeesha, reveals that he kept a journal from twenty years earlier hidden on the island, and warns the Stranger not to let Atrus come after them. Achenar's journal reveals that he and Sirrus planned to trap their mother Catherine on Riven and use a "Memory Chamber", a gigantic flower-like structure used to preserve the memories of the dead, to take control of Atrus' body and steal his knowledge of the Art of Writing. The Life Stone that Achenar stole is used to power the Memory Chambers, leaving the current one in danger of collapse. Shortly afterwards, the Stranger finds Sirrus in an underwater harvester used for collecting memory globes for storing those memories; he blows up the harvester and flees to an older Memory Chamber, decrepit and abandoned. After encountering the Stranger there, Sirrus tells the Stranger that Achenar is the guilty one, and asks the Stranger to find Atrus and bring him to Serenia to set things right.
Finding that the old Memory Chamber door has been locked by Sirrus with a special color-code combination, the Stranger goes to the active Memory Chamber to seek aid from the Serenian Protectors, who believe that the answers can be found in their "mirror realm", known simply as Dream. Obtaining a "spirit guide", the Stranger enters Dream and interacts with their guide, who tells them to interact with the Ancestors, the spirits of all Serenians who have died and had their memories preserved, to bring them into harmony. After bringing the Ancestors into harmony, the Stranger discovers the combination to Sirrus' color-code lock. Returning to the "waking world" and entering the old Memory Chamber, the Stranger finds Yeesha strapped into a chair, and she begs to be released from it with a silver lever. At that moment, Achenar arrives with a crossbow and the Life Stone, and warns that Sirrus used the Memory Chamber to remove Yeesha's memories and transfer his own into her body; Achenar points to an amber lever, which will reverse the mind-transfer.
At this point, as in the other games, the ending varies. Delaying too long will result in Yeesha (who is in fact Sirrus) taking Achenar's crossbow and shooting first him, then the Stranger. The silver lever will release Yeesha (again, possessed by Sirrus), who drops a large stone on Achenar and the Stranger, and then shoots the Stranger dead. In the good ending, the Stranger pulls the amber lever, reversing the mind-transfer process. But because of the age of the Memory Chamber, it becomes unstable; Achenar tells the Stranger to return to Dream and set Yeesha's memories right, while he uses the Life Stone to stabilize the chamber by inserting it into the chamber's shrine, poisoning him with its contained toxic spores. In Dream, the Stranger finds a monstrous creature, representing Sirrus' Dream-form, anchored to Yeesha's essence and preventing her from returning to her body; with no spirit guide, Sirrus is forced to cling to Yeesha to avoid being lost forever. He maintains his anchors by jumbling up Yeesha's memories. The Stranger restores Yeesha's memories and frees her from Sirrus' grasp; Sirrus' Dream-form is destroyed by the shifting waves of Dream, killing him. The Stranger awakens to find Achenar, fatally poisoned, confirming that the transfer was successful; he dies shortly afterward. The Stranger then returns to Tomahna to meet with Atrus, who says that Catherine has taken Yeesha to Tay (the "rebel Age" used to evacuate Catherine's people in Riven), and remarks that while his sons are gone, his daughter is safe.