The Sins of the Wolf — Anne Perry

Nurse Hester Latterly finds herself well suited for the position: accompany Mrs. Mary Farraline, an elderly Scottish lady in delicate health, on a short train trip to London. Yet Hester's simple job takes a grave turn when the woman dies during the night. And when a postmortem examination of the body reveals a lethal dose pf medicine, Hester is charged with murder--punishable by execution.

The notorious case presents detective William Monk with a daunting task: find a calculating killer amongst the prominent and coolly unassailable Farraline clan. Since Hester must be tried in Edinburgh, where prejudice against her runs high, there is little that the highly skilled barrister Oliver Rathbone can do to help. He can only try to direct her Scottish lawyer from the frustrating sidelines, and pray that Hester will not be sent to the gallows....