Early in Camilleri’s superlative 16th mystery featuring Insp. Salvo Montalbano (after The Dance of the Seagull), two reclusive religious fanatics—brother and sister Gregorio and Caterina Palmisano—start firing guns at the “sinners” in the street below their apartment building in Vigàta, Sicily. Montalbano and his team lay siege to the Palmisanos’ house and eventually disarm the elderly couple without bloodshed. Soon afterward, Montalbano finds an envelope addressed to him marked “treasure hunt.” Inside is a short poem that appears to be a riddle, the first of several such messages. While he’s inclined to dismiss them as the work of a crank, a niggling sense of discomfort remains. Meanwhile, a number of bizarre incidents puzzle Montalbano, including the discovery in a dumpster of what at first is mistaken for a woman’s corpse but is in fact a decrepit inflatable sex doll. Furthermore, it’s an exact duplicate of the one Montalbano and crew noticed in Gregorio’s bed the night of the siege. Once again, Camilleri’s sardonic sense of humor distinguishes this Mediterranean crime novel from the pack.