The Secret of the Dragon's Teeth continues the adventures of Gavin Kane, Emily Scott, and Bunty Digby, sixteen-year-olds who struggle with their daily lives in England during the pivotal year of 1944. Cornwall is now an armed camp, with thousands of Americans and Canadians, as well as men from throughout the occupied countries, all training and preparing for the invasion of the European continent. The war has reached a brutal climax and the Allies now have the upper hand. In Nazi Germany, however, Heinrich Himmler is far from admitting defeat, as he prepares to unleash whatever horror he can devise to delay the inevitable.

The Secret of the Dragon's Teeth continues the friendship and alliance between this teenage trio and their wonderful mentor, Thaddeus Osbert. The dragon has proved adroit at looking after the teens, while also juggling the expectations of his own species. Thaddeus commits himself to take an active part in deciding the outcome of the war, while he also discovers that some of his fellow dragons are conspiring against humanity. Right in the midst of the Normandy invasion, Sir Osbert adds his incredible powers to help sway the odds. Likewise, Gavin accepts his role as the wielder of the enchanted sword of King Arthur and finally confronts the evil wizard Adicus Schinagel, with unexpected results.