Alien to the street yet embedded within it, easy to read but impossible to decipher, the Toynbee Tiles are an internationally enigmatic, handcrafted phenomenon. First discovered in the early 1980s, these crudely tiled signs have appeared in pavements all over the world, each uniquely made yet all expressing an identical message: Toynbee Idea; In Kubrick's 2001; Resurrect Dead; On Planet Jupiter. The words seem deliberately, outlandishly cryptic. But as Jon Foy's appropriately DIY, remarkably sincere documentary debut reveals, the truth is both stranger and more straightforward than that. The film's investigation is twofold: to discover the identity of the tiler, and to understand the meaning of his message. Since no one has ever come forward to claim authorship of the tiles, the mystery of the "Toynbee Tiler" has been irresistible to all manner of amateur sleuths. One of them is Foy's main subject and collaborator, Philadelphia outsider artist and musician Justin Duerr. Foy and Duerr follow leads from the Northeast corridor to Buenos Aires, from Internet chat rooms to shortwave radio conventions, from cockamamie conspiracy theorists to playwright David Mamet. Resurrect Dead works splendidly as a threadbare urban mystery, teasing out details and complications without withholding too much information. As Duerr and his associates narrow in on the likeliest suspect, they're inclined to stop short of disclosure. Turned on by a mystery, they start to turn off when faced with an understandable, intimately relatable need to maintain it.