In a field outside of Salzburg, Austria, the mooing of an uneasy cow attracts the attention of her owner. When the farmer goes over to check out what has upset his livestock, he makes a most awful discovery: a woman’s body, a person who had gone missing several days before.

Murder detectives Beatrice Kaspary and Florin Wenninger are dispatched to the scene. Even from a distance, Kaspary’s keen eyes pick up what appear to be markings on the soles of the corpse’s feet. Odd ones. On close inspection, they turn out to be N47° 46.605 E013° 21.718. It doesn’t take the detectives long to recognize them as coordinates, but their colleague Stefan takes it a step further and poses the possibility that the numbers are geocaching coordinates. So what are the police supposed to do with them?

"[P]ut on your thinking cap before you open FIVE, sit back with your calculator and prepare to be shocked. Oh, and you might want to make sure all the curtains are closed and the doors are locked."

Naturally, they follow the tattooed clue in the obvious direction and go in search of the cache. The box, which has been well hidden, contains a very gruesome find. And, of course, a note that sends them off in pursuit of yet another hidden box. Geocaching has become a modern form of outdoor entertainment in recent years. And, as Stefan would point out with a bit of pride, a relatively clean and honest one. So now someone is definitely sullying its reputation. But the murder squad has little choice but to follow the clues that are fed to them. Five coordinates, five clues. Unfortunately, as the clues mount up, so do the bodies.

Are the victims chosen at random, or is there a pattern? Geocaching looked, at first blush, to be a common bond, but connecting the dead people through that hobby has become difficult. So, if not geocaching, then what? Something they all saw? An event they each attended? A certain model car? They find themselves grasping at straws but catching only air. And Kaspary’s boss is riding her hard to find answers. He seems to be a man who believes that women, most especially Kaspary, should not be allowed to go into police work. To make her job tougher yet, the killer has begun to make the murders personal. Luckily for Kaspary, she has the best possible partner. Wenninger always has her back --- with their boss, with their suspects, even off the job. But will that be enough?

FIVE is not a particularly big book, but don’t think that it will be a quick cruise through because it won’t. Sure, you might want to turn the pages one right after another, but this is one of those thrillers to pay close attention to. It’s a smart mystery, with a tortured and torturing murderer whose identity will surprise even the sharpest readers. So put on your thinking cap before you open FIVE, sit back with your calculator and prepare to be shocked. Oh, and you might want to make sure all the curtains are closed and the doors are locked.