Purity in Death (In Death #15)

Louie Cogburn had spent three days holed up in his apartment, staring at his computer screen. His pounding headache was unbearable - it felt like spikes drilling into his brain. And it was getting worse. Finally, when someone knocked at his door, Louie picked up a baseball bat, opened up the door, and started swinging....

The first cop on the scene fired his stunner twice. Louie died instantly. Detective Eve Dallas has taken over the investigation, but there's nothing to explain the man's sudden rage or death. The only clue is a bizarre message left on his computer screen: ABSOLUTE PURITY ACHIEVED
And when a second man dies under near-identical circumstances, Eve starts racking her brain for answers and the courage to face the impossible...that this might be a computer virus able to spread from machine to man....