Witness Joe Pilgrim, recently returned veteran of the conflict in Afghanistan, child of the age of terror, recent convert to a particularly dogmatic branch of Catholicism and newly diagnosed sufferer of post-traumatic stress disorder. Fleeing his family as the terror of his past catches up with him, he crashes his car and is taken to reside within the Isis Trust Home, one of the best, and most secure, mental health facilities in the country. Whilst there he meets Jonah S., renowned physicist, bestselling author of science fiction, outspoken advocate of a hard line brand of anti-theism, and lifelong manic depressive. Delusional, paranoid and befuddled by medication, Jonah S. is nevertheless still a sharp polemicist; as the two patients get to know one another they each question the other's world view, with drastic, deadly consequences.