The School of Darkness (1985) is the only novel-length John Thunstone story as best I can tell. However, a number of shorter works featuring Thunstone have been collected in Third Cry to Legba and Other Invocations.
In this novel, John Thunstone is invited to participate in a seminar on folklore at Buford State College. He learns that the college had been founded by a rich man, Samuel Whitney, in gratitude for the healing prayers of a local women's group. However, other accounts state that Whitney had been cursed by his enemies and healed by a coven of witches. Moreover, two or more covens are supposedly still active in Buford. Grizel Fian, a fellow particiant in the seminar, is mentioned as the head of one coven.
Other participants include a Cherokee medicine man, a Catholic priest and a Japanese scholar. Lee Pitt, a professor of English at Buford State, is host of the seminar. Sharon Hill, the Countess Monteseco, also appears at the seminar; Sharon and Thunstone have a long standing friendship and have faced danger together. Although John loves her, he does not want her to be placed at risk and tries to discourage their relationship.
Soon after his arrival, Thunstone receives a threatening phone call. At dinner that night, Grizel asks about Rowley Thorne, an old enemy of Thunstone, who had literally disappeared into thin air during their last encounter. Afterward, Thunstone sees Grizel signal a man who reminds him of Thorne.
This novel shows its age in the characters and plot, particularly in the relationship between John and Sharon. However, it is an superior example of pulp fantasy and a fairly enjoyable story. Recommended for all Wellman fans and anyone who enjoys old fashioned supernatural thrillers.
-Arthur W. Jordin