Friday night fever in the cities of Brazil is not so much about disco-dancing as spirittrancing. It is when the 30 million practitioners of Umbanda, a voodo-like cult that started this century, perform their strange rites. Umbanda, a synthesis of African and Amerindian gods with Catholicism, is Brazil's fastest-growing religion. At spiritist centres, like those run by Abraham in the slums of Rio, or Marilda or on luxurious Governor's Island, possession states are used to grant favours, cure illness or lift curses. The Catholic Church, once vehemently anti-Umbanda, now tolerates it. But for the new evangelical churches, toleration is an anathema: their Friday night services are a spectacle of mass exorcism, a battle between God and the Devil.