Velocity starts with death by garden gnome and gets weirder from there.

The back of the book has the message: "If you don’t take this note to the police and get them involved, I will kill a lovely blond schoolteacher. If you do take this note to the police, I will instead kill an elderly woman active in charity work. You have four hours to decide. The choice is yours." Going on that piece of information alone, one might think that Velocity will be a typical "ticking time bomb" type thriller; it isn't.

Bill Wile is more of an antihero than protagonist. He wants nothing to do with this secret person taunting him and framing him for murders. Because of his own shady past he doesn't feel comfortable going to the police even though he wants to.

For observant readers, Koontz leaves lots of clues. They are hidden in plain sight. This is not a connect the dots mystery but one a second reading, the clues are there, popping out from the most unexpected places.