Enlarge (credit: Detail from the cover of Underground Airlines)

Most alternate histories reverse just a few big historical events. They show us how bad things would be if the Nazis won World War II or the South won the Civil War. Though Ben H. Winters’ new novel Underground Airlines treads familiar territory in this respect, few alt histories are as complex and horrifying as it is.

Underground Airlines is set in a 2016 where slavery is still legal in part of the United States. In this reality, Abraham Lincoln was assassinated in 1861, and the Civil War never happened. Instead, a compromise was struck. To this day, four Southern states (the “Hard Four”) still keep human beings as property.

The book’s main character, who mostly goes by Victor, is an African-American who works as a “soul-stealer”—basically, he’s a bounty hunter who returns escaped slaves to the Hard Four. He works for the Federal Marshals, and he’s the kind of manipulative, coldly efficient monster that often populates films noir. But as he remembers his own experiences as a slave in the South, he starts to question what he does.