The Arnolfini Portrait is at the center of this book, the great van Eyck painting of a merchant and his wife in the center of Bruges. Around the painting swirls a galaxy of esoteric and entertaining knowledge of saints' days, herbal cures, animal symbolism, miracles, and transformations.

Shamrock Tea, the magical substance that allows people to experience the world with visionary clarity, can only be found by passing through the van Eyck painting. The characters who bear this knowledge include young Carson, his uncle Celstine, his cousin Berenice, Ludwig Wittgenstein, Father Browne, and the young Maeterlinck, nephew of Maurice Maeterlinck, an art-dealer in the Belgian city of Ghent. Everything connects with everything else: one of the book's presiding geniuses is Arthur Conan Doyle, who believed you could read the world in a drop of water. Shamrock Tea is an homage to this idea, to an enchantingly medieval sense of the unity of the world - what in other words we call magic.