All old cities have their secrets.

Early morning, August 1882. Inspector Aloysius Allaway is awoken and brought into the investigation of a strangely dressed young woman found in King's Chapel Graveyard while 138 years later rookie Detective Shiloh Amsel finds a mummified human heart.

Two different crimes, connected by Echo Cross, Boston's most closely kept secret. A hidden neighborhood, refuge of fae and supernatural beings, becomes the center of a conspiracy linking both detectives to a dark world of cults, conspiracy, and curious rifts in time.