This book is an excursion into Britain's bloodstained, power-obsessed past. The author's investigation into Lord Darnley's murder is set against one of the most dramatic periods in English history. Its conclusions shed light on the actions and motives of the conspirators and, in particular, the extent of Mary's own involvement. Tall, handsome, accomplished, and charming, Henry Stuart, Lord Darnley, had it all, including a strong claim to the English throne, a fact that threatened the already insecure Elizabeth I. She therefore opposed any plan for Darnley to marry her cousin, Mary, Queen of Scots, who herself claimed to be Queen of England. But in 1565 Mary met and fell in love with Darnley and defied Elizabeth by marrying him. It was not long before she discovered that her new husband was weak and vicious, and interested only in securing sovereign power for himself. On February 10, 1567, an explosion at his lodgings left Darnley dead.

There were many who might have had a motive for murdering him, not least Mary herself. The intrigue thickened after it was discovered that apparently he had been suffocated before the blast. Emerging from the tragedy were more mysteries than any historian has ever satisfactorily solved. Mary and Darnley's marriage had been an adulterous disaster. After Darnley's death, Mary showed favor to the powerful Earl of Bothwell, causing her enemies to accuse her of being his partner in both infidelity and murder. Mary insisted that the murder conspiracy had been aimed at her, and that she had escaped only by changing her plans at the last minute. It has even been suggested that Darnley himself had planned the explosion in order to kill her. The murder of Darnley ultimately led to Mary's ruin. After her deposition, there conveniently came to light a box of documents, the notorious Casket Letters, that her enemies claimed were proof of her guilt.

But Mary was never allowed to see them, and they disappeared in 1584. The question of their authenticity has haunted historians ever since. After exhaustive reexamination and reevaluation of the source material, the author has come up with a solution to this enduring mystery that can be substantiated by contemporary evidence, and in the process has shattered many of the misconceptions about Mary, Queen of Scots.