It's been five centuries since Pedro de Alvarado, a homicidal Spanish conquistador, seized from the Maya the volcanic realm that became Guatemala. But his bloodlust still haunts the country, which today has one of the highest homicide rates in the western hemisphere. Guatemala's 36-year-long civil war, which ended in 1996, killed 200,000 people. Its cloak-and-dagger murders have made locals so paranoid that "even the drunks are discreet," as one 19th century visitor wrote.
That neurosis still shrouds Guatemala City, a gloomy capital that no amount of marimba music can brighten. Rich and poor communities alike are surrounded by walls topped with...