The Mapmaker's Secret

Olivia Mercer, a map authenticator in Boston, discovers a 17th-century map depicting a city that never existed. As she investigates, she uncovers a secret society of cartographers who believed they were mapping "thin places"-locations where the boundary between worlds was permeable. But when a series of gruesome murders suggests that someone is using the maps to open these doorways, Olivia realizes she's stumbled onto a conspiracy far more dangerous than she ever imagined.

With the help of a...