Louisville, Ky., four-piece Slint generated music over the course of a few short years in the late ’80s and early ’90s, culminating with two albums: Tweez (1989) and Spiderland (1991). The band broke up before almost anyone outside of their hometown was aware they existed. As years went on, the haunting, intimate, pensive music on Spiderland steadily earned new listeners, who in turn became devotees — then obsessives. The absence of activity from this band only heaped mystery upon a mystery: Who created this work? Where did they find their inspiration? Where did they go? Breadcrumb Trail, director Lance Bangs’ documentary film, shines some light on a few but not all of these questions.