A secret chamber. A mysterious shipwreck. A murder in the desolate salt marshes.

A seemingly quotidian private case turns out to be more sinister than Special Agent A.X.L. Pendergast ever could have imagined.

Pendergast, with his ward Constance Greene, has arrived in Exmouth, Massachusetts, to investigate the theft of a priceless wine collection. But inside the cellar, they find something considerably more macabre: a bricked-up niche clearly built to hold a body, now suspiciously bare. Could it be the robbers real aim was to remove a mouldering skeleton?

Exmouth is a town with a grim past, and this skeleton may be testament to an ancient transgression. When a murdered corpse is discovered in the surrounding salt marshes, Pendergast will have to wonder if the sins of the past live on...