Penelope Salvo has spent the last year trying to find her way off Earth and down into the depths of Hell. At every turn, the archangels Metatron and Zophiel - the Countenance of Peace and the Spy of God - show up to ruin her plans. Not to be daunted, Penelope turns to her old friend Tengoku, the host of Unknowable Yellow, for help. What follows is a multi-dimensional journey that takes Penelope to the Voodoo afterlife, the Land of Oz, New Beatlemania, and a myriad of other strange worlds.Penelope Salvo and Unknowable Yellow expands on the events of Penelope Salvo and Impossible Red and Penelope Salvo and Untouchable Orange. She finds herself partnered up with Madam Brijit who is on her own personal journey to discover the whereabouts of her lost husband Baron Semedi. They begin their journey as enemies, but constant danger forces them to learn to work together.