In the summer of 1958, Dave Robicheaux and his half-brother Jimmie are just out of high school. Jimmie and Dave get work with an oil company, laying out rubber cables in the bays and mosquito-infested swamps all along the Louisiana-Texas coastline.

But on the Fourth of July, change approaches in the form of Ida Durbin, a sweet-faced young woman with a lovely voice and a mandolin. Jimmie falls instantly in love with her. But Ida's not free to love - she's a prostitute, in hock to a brutal man called Kale.

Jimmie agrees to meet Ida at the bus depot, ready for the road to Mexico. But Ida never shows. That was many years ago.

Now, an older, well-worn Dave walks into Baptist Hospital to visit a man called Troy Bordelon, who wants to free himself of a dark secret before he dies. A bully and a sadist, he has a lot to confess to - but he chooses to talk about a young girl, a prostitute who he glimpsed briefly as a kid, bloodied and beaten, tied to a chair in his uncle's house.