In this story about the battle between good and evil over possession of the Holy Grail (or Graal), the primary representatives are Julian Davenant, Archdeacon of Fardles church, on the side of good, versus Gregory Persimmons, the owner of a publishing firm, for evil. A supernatural figure, Prester John, also intervenes on behalf of the virtuous and rescues the Grail. Each side has a few allies, and there are several innocent victims caught in the middle.

Julian Davenant, the archdeacon, is a plump, apparently innocuous man who is deeply devoted to God. He takes extraordinary steps to protect the Grail, but also agrees to sacrifice it to save Barbara’s life. He risks his life to steal it back from Gregory. Once the vessel is restored to Prester John’s care, Davenant dies peacefully in his church.

Kenneth Mornington, an editor at the Persimmons firm, first shows Julian a manuscript claiming the Grail is at Fardles church. Becoming Julian’s devoted ally in rescuing the chalice from Gregory, he falls subject to a black magic ritual and loses his life.

The Duke of North Ridings, a nobleman in the Fardles area, joins Mornington to save the chalice and, with it, Julian’s life.

Prester John, a legendary priest-king, embodies the Grail’s keeper, thus representing the validity of its heavenly domain. When Barbara is injured, he appears as a mysterious stranger at Fardles. At the novel’s end, after he celebrates Mass, the chalice disappears with him.

Lionel Rackstraw is an editor at Persimmons’s firm. He; his wife, Barbara; and their son, Adrian, are invited for a weekend at Gregory’s country home. During their stay, Gregory injures and then poisons Barbara with an ointment, causing a mental breakdown. Adrian’s purity draws Gregory’s desire to indoctrinate him into the black arts.

Gregory Persimmons owns the publishing house but has retired from running it, a job done by his son. Gregory’s lust for power and involvement in black magic are superficially obscured by his benign public demeanor and apparent kindness to the Rackstraw family. Harsh and demeaning treatment of his son, however, reveals his true character. He will stop at nothing, even murder, to gain possession of the Grail.

Manasseh, often referred to as “the Jew,” is one of Gregory’s accomplices; he impersonates a doctor to treat Barbara Rackshaw.

Dimitri Lavrodopoulos, or “the Greek,” is also Gregory’s accomplice. In his London shop, the black magic ritual diagrams are drawn around the hidden chalice.

James Pattison is a former accomplice of Gregory. After he repented, Gregory murdered him.