Dementium II features many improvements over its predecessor, including different weapons, a larger variety of enemies, the ability to jump and crouch, save points, more environments, the ability to hold the flashlight and gun at the same time, an improved map system and the removal of respawning enemies.

Suddenly, the world around William changes into a demented version of its usual appearance, and he is forced to fight his way through this altered reality.

As William progresses reality shifts from normal to demented semi-frequently, and occasionally more postcards from himself show up, giving him direction and advice.

Afterwards, William continues looking for a way out of the hospital, eventually stumbling upon his intake form, which claims he murdered his wife, and is suffering from a "schizotypal disorder" or some unknown mental illness.

This leads him to his daughter's grave, from which he digs up a doll, and brings it to a church where his wife is supposed to be waiting.

In the hospital, William finds a page from a book that speaks of Malatesta, an ancient serpent trapped within the Plane of Anguish.

[19][20] In Japan, where the DS version was ported and published by Intergrow on September 30, 2010,[citation needed] Famitsu gave it a score of one eight, two sevens, and one eight for a total of 30 out of 40.