'Let's go take a look.'
Two crime-scene techs in blue Windbreakers were working inside the tape line, along with a medical examiner whom I easily recognized from behind.
Porter Henning's unofficial nickname is 'Portly,' and, widthwise, he makes 'Man Mountain' Sampson look practically dainty. I've never been sure how Porter squeezes into some of those tighter crime scenes, but he's also one of the most insightful MEs I've worked with.
'Alex Cross. Gracing us with your presence,' he said as I walked up.
'Blame this guy.' I thumbed at Sampson but then stopped short when I saw the victim.
People say the extreme stuff is my specialty, which it kind of is, but there is no getting used to human mutilation. The victim had been left faceup in a clump of bushes. The multiple layers of dirty clothes marked him as homeless, maybe even someone who slept right there in the park. And while there were signs of a severe beating, it was the numbers carved into his forehead that made the biggest impression. As in the previous murder, it was almost too bizarre.
2^30402457-1
'Are those the same numbers as the last time?' I asked.
'Similar,' Sampson told me, 'but no, not the same.'
'And we don't know who the victim is?'
John shook his head. 'I've got guys asking around, but most of the bench crashers made themselves scarce as soon as we showed up. It's not exactly a trust fest around here, you know?'
I knew, I knew. This was part of what made homeless deaths so hard to trace.
'There's also the shelter just a few blocks up on Thirteenth Street,' John went on. 'I'm going to head up there after this, see if anyone knows anything about this man.'
The scene itself was hard to interpret. There were fresh footprints in the dirt, flat soles as opposed to boots or sneakers. Also, some kind of grooved tracks, maybe a shopping cart, but that could have been completely unrelated. Homeless folks rolled through here all day, every day. All night, too.
'What else?' I asked. 'Porter? You find out anything yet?'
'Yeah. Found out I'm not getting any younger. Other than that, I'd say cause of death is tension pneumothorax, although the first strikes were probably here, here, and here.'
He pointed at the crushed side of the dead man's head, where a pink ooze had filled his ear. 'Basal skull fracture, jawbone, zygomatic arch, the whole frickin' works. If there's any silver lining, the poor guy was probably out cold when it happened. There's track marks all over him.'
'All just like the last time,' Sampson said. 'Has to be the same perp.'
'What about the cutting on the forehead?' It was the cleanest knife work I'd ever seen. The digits were easily readable, the cuts shallow and precise. 'Any initial thoughts about the cuts, Porter?'
'This is nothing,' he said. 'Check out the real masterpiece.'
He reached down and rolled the young man onto his side, then lifted up the back of his shirt.
'You've got to be kidding.'
The math equation covered the whole area from his waistband to his shoulder blades. I'd never seen anything like it. Not in this context anyway. Sampson motioned the scene photographer over to get a shot.
'This is new,' John said. 'The last numbers were just on the face. Makes me wonder if our guy's been practicing. Maybe other bodies we haven't found.'
'Well, he definitely wanted you to see this one,' Porter told us. 'That's the other thing. There's not near enough blood here for the amount of blunt force trauma. Someone pounded this kid, then brought him here, and then did the fancy knife work.'
'Doo-doo, doo-doo.' The photographer let out a snatch of The Twilight Zone theme before Sampson stared him down. 'Sorry, man, but… damn, I'm glad I don't have your jobs today.'
Him and everyone else.
'So the question is, why bring him here?' Sampson said. 'What's he trying to say to us? To whoever?'
Porter shrugged. 'Anyone speak math?'
'I know a prof at Howard,' I said. 'Sara Wilson. You remember her?' John nodded, still staring down at those numbers. 'I'll give her a call if you want me to. Maybe we can head up there this afternoon.'
'I'd appreciate it, that'd be good.'
So much for my quick consult. I had no time for this, but God help me, now that I'd seen the damage this perp was capable of, I wanted a piece of him.
Chapter 58
I'D KNOWN SARA WILSON for more than twenty years. She and my first wife, Maria, were freshman roommates at Georgetown and remained good friends until Maria's death. Now it was just Christmas cards and the occasional chance meeting between us, but Sara hugged me hello when she saw me and still remembered Sampson by name – first and last.
Her tiny cell of an office was in the unimaginatively named Academic Support Building B on the Howard campus. It was crammed with bookshelves to the ceiling, a big sloppy desk just like mine, and a huge whiteboard covered in mathspeak, in different colors of dry-erase marker.
Sampson took the windowsill, and I sat down in the lone guest chair.
'I know you've got exams coming up,' I said. 'Thanks for seeing us.'
'I'm happy to help, Alex. If I can help?' She tipped a pair of rimless specs off her forehead and looked down at the page I'd just handed her. It had transcripts of the numbers and equations that were found on the victims. We also had crime-scene photos with us, but there was no reason to share the gory details if we didn't have to.
As soon as she looked at the page, Sara pointed at the more complicated of the figures.
'This is Riemann's zeta function,' she said. It was the one we'd seen that morning on John Doe's back. 'It's theoretical mathematics. Does this really have something to do with one of your cases?'
Sampson nodded. 'Without going into too much detail, we're wondering why this might be on someone's mind. Maybe obsessively.'
'It's on a lot of people's minds, including mine,' she said. 'Zeta's the core of Riemann's hypothesis, which is arguably the biggest unsolved problem in mathematics today. In the year two thousand, the Clay Institute offered a million dollars to anyone who could prove it.'
'Sorry, prove what?' I said. 'You're talking to a couple of high school algebra cutups here.'
Sara sat up straighter, getting into it now. 'Basically, it's about describing the frequency and distribution of all prime numbers to infinity, which is why it's so difficult. The hypothesis has been checked against the first one and a half billion instances, but then you have to ask yourself – what's one and a half billion compared to infinity?'
'Exactly what I was about to ask myself,' Sampson said, straight-faced.
Sara laughed. She looked almost exactly the same as she did back when we were all pooling our pocket change for pitchers of beer. The same quick smile, the same long hair flowing down her back.
'How about the other two sets of numbers?' I asked. These were the ones that had been carved into the victims' foreheads.
Sara glanced down for a second, then turned to her laptop and googled them from memory.
'Yeah, right here. I thought so. Mersenne forty-two and forty-three. Two of the biggest known prime numbers to date.'
I scribbled some of this down while she spoke, not even sure what I was writing. 'Okay, next question,' I said. 'So what?'
'So what?'
