This number depends directly on how many books in the series have been completed ("Kai rank").

In this book, Lone Wolf is charged by the King of Sommerlund to investigate the disappearance of a troop of cavalry.

The cavalry, led by a man named Captain D'Val, themselves disappeared under mysterious circumstances while investigating a disruption in the flow of mined resources from the province of Ruanon.

Lone Wolf, along with the fifty Sommlending soldiers who accompany him, must uncover the truth surrounding the missing men and stop the resurrection of an ancient and terrible evil.

Colin Greenland reviewed The Chasm of Doom for Imagine magazine, and stated that "You can start here, but you'd be much better off going back to the first two and equipping yourself with the almighty Sommerswerd, a heavy duty blade if ever there was one.