[1][2] It is set in the same fictional "Thousand Worlds" universe as several of Martin's other works, including Dying of the Light, Sandkings, Nightflyers, A Song for Lya and the stories collected in Tuf Voyaging.
[3] Damien Har Veris — a priest skilled in resolving heretical disputes efficiently, although now spiritually exhausted — is sent by his alien archbishop as Knight Inquisitor to deal with a particular sect that has made a saint of Judas Iscariot.
Arriving on the sect's distant planet on board his ship, the Truth of Christ, Har Veris confronts its heresiarch, Lukyan Judasson, creator of the Way of Cross and Dragon narrative, but finds that he is already expected.
Questioning Judasson, Har Veris uncovers a conspiracy of nihilistic Liars, who see Truth as entropy and despair, and who wish to soften and color the ultimately meaningless lives of others by creating belief in carefully crafted Lies.
Har Veris then uses political manipulation and the public's fear and distrust of psychic powers to turn the tide on the Judas cult, resolving yet another heresy with dispatch.