Story
This section contains spoilers which could ruin the game for you if you have not played it before, or have not yet reached the end.
It has been decades since Atrus and his wife were betrayed by their own sons, Sirrus and Achenar. It has been decades since Atrus and Catherine were freed by a stranger who discovered the Myst book dropped into the Fissure [see: Book of Atrus].
In a fit of anger Atrus burnt the Linking Books that lead to the Ages in which Sirrus and Achenar were imprisoned. For years Atrus has been keeping a secret, the secret that his sons still exist. Calling his friend “The Stranger” to Tomahna, Atrus explains that he only burnt the Linking Books to the Ages not the Descriptive Books. After a malfunction in his lab whilst showing “The Stranger” his new Crystal Viewer, Atrus travels to Rime to get some replacement parts.
On Tomahna “The Stranger” looks after Yeesha until an explosion rocks Atrus’ home and Yeesha goes missing. Sirrus has escaped, Achenar too and they have taken Yeesha to the Age of Serenia. The Stranger navigates the Prison Ages of Haven and Spire gathering the information he needed to stop the brothers. The Stranger follows them to Serenia where its discovered that Sirrus plans to use the properties of the Age to inhabit the mind of Yeesha and learn the Art from Atrus. With the help of Achenar, “The Stranger” saves Yeesha, but not without a cost. With his mind trapped in Dream, Sirrus body could no longer survive and so he passes away. Upon breaching the core chamber of device used by Sirrus, Achenar is subjected to toxic fumes. Returning to Yeesha and seeing her freed, Achenar collapses upon her lap and dies.
With Yeesha saved, The Stranger returns to Tomahna to notify Atrus of the deaths of his two sons.
