Heading back to work the day after she returns from her European honeymoon, Delaney Nichols is excited to get back to the Cracked Spine. But as she disembarks the bus and hurries toward the shop, she and another woman collide, sending a stack of books the woman is carrying to the ground.

Delaney's hapless victim's name is Mary, and she and Delaney can't help but notice that they bear an uncanny resemblance to one another. According to Mary, they both also look like the long-beheaded Mary Queen of Scots. Even stranger, Mary believes she is reincarnation of the Scottish queen. But peculiar as Delaney's doppelganger is, she doesn't have time to dwell on it: On her arrival to the bookshop, she learns the Edinburgh city council wants to close the Cracked Spine, citing code violations, and she's determined to stop them.

But when Mary's husband dies in a car explosion - and Delaney learns he was the very member of city council who proposed that the city take a closer look at the bookshop's construction - she starts to wonder if her meeting with Mary wasn't an accident. Edinburgh has become as filled with intrigue and deception as any European court, and Delaney is determined to get to the bottom of this royal mystery.