After her entrance into the realm of Biblical fiction, Caldwell produced Great Lion of God (1970), in which Lucanus appears as a character. He also appears in Caldwell's novel with Jess Stearn, I, Judas (1977), where Judas is seen as Christ's challenger rather than his betrayer, searching for the militant Messiah to free the Jews from Roman domination and attempting to force Jesus to action.

On the heels of Dear and Glorious Physician came the first volume of her metaphysical trilogy, The Listener (1960), followed by No One Hears But Him (1966), and Dialogues with the Devil (1967). In the latter book, where she acknowledges the presence of an alien inspiration which took over the writing midway through, the archangel Lucifer warns man that he cannot escape the fate of Venus and Mercury, once peopled but now destroyed.

Her fascination with Roman times is evident in her 1965 best seller A Pillar...