We'd noticed some new spray-painting on popular corners in the Mission, but didn't actually look at them until folks in the SFist Tips column passed along the word that it's part of a Choose Your Own Adventure graffiti piece.

We didn't manage to figure out where it starts, but there's some good entries near Dolores Park and Tartine, and here's the one we found on 17th and Mission. There's a picture set on Flickr too (which says one part of the story starts at, of course, 16th and Valencia.)