Satan, wants her daughter Laura (Betsy's half-sister), who is the antichrist, to visit Hell so she could understand her heritage. But Satan says Laura would need Betsy to accompany her so that Laura can get to know Betsy better. Betsy agrees, but only under the condition that Satan fix things so that Betsy can read the Book of the Dead for more than just a few minutes. Reading it for more than a few minutes at a time drives a person insane.
Betsy and Laura visit Hell, which results in a time-travelling journey that reveals the history of Betsy's husband, Sinclair, and that has some serious consequences.