The Speciman by Jaima Fixsen

Walk carefully, lest you become a part of Dr. Burnett's collection…

1826. Isobel Tait finds herself, by chance, staring at a tiny human heart floating in a jar. It should be of little consequence; Dr. Burnett is renowned for his collection of oddities and medical specimens, and this, a juvenile heart with a damaged mitral valve, is not the strangest thing on display. Except that the condition is rare, and that Isobel's young son, who has been missing for months, suffered from the ailment.

A phantom pulse beats in Isobel's ears. She knows something here isn't right.

Missing persons cases are all too common in Edinburgh, where people simply vanish like mist. But Burnett is obsessed with his specimens – how far would he go to acquire a new one? Determined to investigate, Isobel joins his staff as the keeper of his collection. What she'll unearth, though, is far worse than any of her nightmares…

Based on true crimes, The Specimen is a mesmerizing story about one woman's search for truth and vengeance in the darkest of places—where the deadliest secrets lie hidden in plain sight, on a freshly dusted shelf.