After nearly being assassinated, Laharl orders a Prinny to do track down the culprit. The Prinny happens to have a special clock that lets him possess other Disgaea characters to read their thoughts. Flonne, Etna, Gordon, and a bunch of characters from Disgaea: Hour of Darkness are in the story. By sneaking into minds and talking with other Disgaea characters Prinny should be able to identify who tried to kill Laharl.
Disgaea Infinite is an interactive story, not a strategy RPG like the other Disgaea games. NIS America is publishing a visual novel, a genre few North American companies dare to try on consoles. Look for Disgaea Infinite in May.