'Zanzibar. The name itself, languid and conspiratorial, was a kind of illusion. It seemed to speak of the heart's desire, of that yearning for paradise which is itself a sign we are fallen - that we are in the dirty realm of history, of actuality, of fact.'The year is 1998. Nick Karolides is a marine biologist working on coral reef protection off Zanzibar - the East African island of slaves, sultans and spices that for centuries has signified both the exotic and the malevolent. On a trip to