a Monday afternoon in December 2001, a pair of police officers walked in the side door of a big old farmhouse in the woods in Loudoun County, Virginia. They had just received a frantic 9-1-1 call from a man who said he had found his neighbor horrifically injured on the kitchen floor. The police officers crept through the house, peering cautiously around corners in case the attacker was still in the house. But other than the sound of their footsteps creaking on the hardwood, the home was completely silent. When they made it to the kitchen, they stopped. There, lying on his stomach, was the body of an older man, covered in blood. One of the officers stepped forward and knelt down to check the man’s pulse, but it was obvious to both of them that he was dead. The officer was about to stand back up, when something strange on the back of the man’s neck caught his eye. Slowly, the officer reached out a hand, and pulled down the collar of the man’s shirt. When he saw what was there, he looked back at his partner with an expression of fear