Requiem, like Brethren and Crusade before it, follows Will Campbell, a Templar involved in a secret order known as the Anima Templi.

After the Fall of Acre, Will returns to Europe to find out that his order agreed to help King Edward I to conquer Will's homeland, Scotland.

The novel received a mixed response from reviewers, with most citing the story's disjointed nature and disparity with the rest of the trilogy as the novel's shortcomings.

[2] In a similar review for The Daily Telegraph, Toby Clements stated that "Young's prose is fine, and the plot is satisfyingly complex, but in the end this book lives or dies on your attitude to the Templars, and in particular, the much romanticised William Wallace.".

[3] A. Jurek, of Curledup.com, was more critical of this concluding novel, stating that "Campbell's story essentially meanders through historical events such as the rebellion of William Wallace, sometimes drowning beneath the surface other story lines and events as he writhes purposelessly for many pages" and, with respect to the novel as a whole, opined "all this is a disappointment because Young can write better; in Crusade, she sets a time bomb ticking in the very first chapter, and the book is a thrill to read.