Ah, early October. Visitors flock to New England from miles around to see the region's famed foliage turn colors. One such group is the Novitiate of Pious Logicians, a group of monks dedicated to monoveritous breviloquent conversation (i.e., the monks are a mix of truth-tellers and liars).
During the NPL's visit to the Laxa Curité Museum, a priceless emerald necklace (the Houquansyntentl necklace) was stolen. Security cameras have revealed that the culprit dressed as a monk, then joined the group after the burglary. Your staff has brought the monks in, and tried to take statements from them, but none would make more than two statements, and none very helpful. With no way to tell the impostor from the real monks, you fear the worst: the thief may get away scot-free.
At least, until an observant beat cop in the Boston Common found an apparent puzzle on NPL stationery. Reading the monk's by-laws, you discover that the monks may construct puzzles and hide statements or secret messages, as long as the statement confirms to that monk's vow. (Clues and instructions however are not constrained in this manner.)
Playing a hunch, you've sent police to each park that's part of the Emerald Necklace, and so far four puzzles have been found. Unfortunately, only one of these four is signed by the author. You and staff begin solving, hoping more puzzles turn up.
Solutions to the puzzles and metapuzzle