Robert Llewellyn, a self-described atheist, sets out to work out which of the world's big four monotheistic religions has the most money: Anglicanism, Catholicism, Judaism, and Islam. He starts at Canterbury Cathedral, where Church of England accounts turn out to be public record, then moves to Westminster Cathedral and finds the Vatican far less willing to open its books. In Jerusalem he tries to pin down synagogue wealth and gets nowhere with the Israeli government either, prompting Ariel Catane of the National Authority of Religious Services to joke that nobody can even agree on how many synagogues there are. At the East London Mosque he finds workable figures for one institution but hits a wall trying to audit the UK's roughly 1,600 mosques, and foreign embassies stonewall him on global Islamic income. Llewellyn treats the stonewalling itself as data, using each institution's willingness or refusal to disclose as a clue to what it might be hiding, before landing on a final tally of who comes out on top.