Jeremiah is elusive in the sense that his actions and abilities and psyche could never quite be comprehended after his life was blown off a normal, predictable course when he was picked up and let down safely by a tornado. After this event, Jeremiah gave up every material thing he had previously valued and devoted himself to a spiritual reality that was difficult for others to value with him. His experience strikes chords of similarity with the epiphany of Martin Luther who, in a powerful lightning storm, had his own epiphany and afterward devoted himself to a religious life as a monk (from that came the call to the Protestant Reformation through Luther's Ninety-Five Theses). Jeremiah was elusive in the same sense that his tornado experience was elusive, as Davy says, "I know it happened. It just shouldn't have."
Jeremiah's elusiveness is also bound up in his inability to give an explanation for his "change in ambitions" after being carried by the tornado. His one explanation is, "I was treated so gently up there." His elusiveness is also in the psychological and physiological changes that came over him as exemplified by when he saved Davy's girlfriend and his face glowed with an unearthly luminosity while he fought off the villains, Pinch and Basca. His elusiveness stems from the elusiveness of what he lived through:
[Jeremiah] was baptized by that tornado into a life of new ambitions. ... Having been ... swallowed by the wrath of God and been kept not just safe but unbruised inside it ...."