An author describes events that may or may not have occurred in reality, concerning an acquaintance with a dual personality as Martin Graham and Gareth Carpenter. Carpenter was as completely truthful as any human being generally can be; Martin, introduced as such, the complete opposite.
Carpenter, having reluctantly taken the part of a Satanist in a school dramatic production, feared that a near-impossible run of ostensibly good luck in his alternative persona might have resulted from a malign influence and tried unsuccessfully to distance himself from it. The author, present at Carpenter's death after an accident and entrusted with commissions on his behalf, suspects that he may have inherited it.