Many millions of people who were raised Catholic have left the church due to the Church's repressive sexual doctrines. But what if a renegade pope tried to radically change the sexual teachings of the Church? Is the Pope Catholic is a story about two Catholic priests in different parts of the world who independently become fed up with their Church's miserable attitude toward sex. Of course, they are both unofficially censured for holding these heretical beliefs. One priest in San Francisco is quarantined by making him chaplain to a foundling home convent of deviant nuns, who he surreptitiously turns into sacred prostitutes to pay expenses. The other priest is a renegade bishop from Amsterdam who gets elected pope because the College of Cardinal's sacramental wine is spiked with Ecstasy (MDMA). He chooses the unusual name, Galileo the First. Soon after the election, the two radical priests meet by chance in Rome, and together they spark a new reformation that puts unrestricted pleasurable sex into Catholicism much as it was in ancient pagan fertility religions. Sacred prostitute nuns, marrying priests, lay "sextants" and many other kinds of sacramental sexual activities are officially inserted into the Catholic liturgy by means of "infallible" ex-cathedra papal encyclicals.

The pope marries a Wiccan witch in a nude ceremony in the Sistine Chapel. Of course, the Catholic world goes crazy. But the attempt to officially put sexual pleasure into Catholicism turns out to be much more complicated than reformers imagine, and is violently opposed by conservative Vatican forces, including a resurrected version of the Inquisition.