Outlast slipped from April to May, but don't think you'll be safe for too long. The PC and PS4 asylum horror admits its first piece of additional content on May 6, although PS4 users in Europe get an extra day of sanctuary until May 7.
The unfortunate soul you play in Whisteblower is Waylon Park, a software engineer who's contracted to work at the Mount Massive Asylum prior to the events of the game. After seeing what unscrupulous things the staff's getting up to, Park feels compelled to expose the establishment to the press. If you've played Outlast, you of course know that his plan went perfectly and everybody lived happily ever after. Especially this (probably NSFW) guy.