The Witness

From publisher blurb:

This is a new collectible RPG in a Golden Age Superheroes vein: to play, you just need any set of the playbooks, with at least one per player. Each playbook gives you a pre-made character and all the rules needed to play them or to run the game for others.

From Introduction:

Exclusive story: the Secret Origin of...The Witness!
Ace private eye Grant Goode was on the case, but took a bullet to the head in a shoot-out with a murderer. The shooter died, but Grant survived, only the bullet lodged in his brain had greatly enhanced his perception and intelligence! Now by day he works cases for his clients, but by night he dons the mantle of The Witness and engages in his own investigation of the city's worst villains!