Developer Vogelsap has announced that The Flock, a first-person asymmetrical multiplayer horror game, will come to Steam in Q3 2015 for a limited time. The length of time the game will be available for depends on the death rate of players within The Flock.
Take a look at the new screenshots:
And, here is the closed Alpha trailer:
Only players who have The Flock in their Steam library will then be able to partake in the yet to be announced climactic finale. After the ending, the game will go offline permanently and no longer be playable.
Source: Press Release