For on the skeleton's finger is a beautiful emerald ring that once belonged to Lucrezia Borgia, the most powerful - and most evil - woman of the Renaissance.
Hours later the skeleton has vanished and one man is dead.
For DCI Jack Pendragon - newly transferred from Oxford to Brick Lane - it's a first case he could have done without. And with two more gruesome deaths in quick succession, it's clear there's a killer out there with a deadly compulsion.
A killer drawing his murderous inspiration from a 15th-century family whose cruelty and depravity knew no limits.