Layton's Mystery Journey: Katrielle and the Millionaires' Conspiracy is a puzzle video game developed by Level-5 for Nintendo 3DS, iOS, and Android. It is the seventh main entry in the Professor Layton series and follows a new protagonist, Katrielle Layton, who searches for her missing father Professor Hershel Layton. The smartphone versions of the game was released worldwide on July 20, 2017; the Nintendo 3DS version was released in Japan on the same date, and in North America and Europe it will be released in October 2017.