In July 1998, at a small Italian restaurant in Queens, New York - an old-school trattoria on Astoria Boulevard called Theresa's - a man named Paul Ferrone, a retired NYPD detective, met with two of his oldest friends.

    The three men had been meeting at Theresa's every month for the past four years, mostly for two reasons. One, Theresa Colopinti's chicken with peppers was the best in the city of New York. More importantly, the second reason was that these three men genuinely enjoyed each other's company.

    After their entree plates were cleared, they began to talk about murder, as was their custom. Cold-case murder. Paul Ferrone's two friends - Matt Grayson, a retired forensic dentist from Newark, New Jersey, and Eli O'Steen, a retired judge from Brooklyn - had been thinking about forming a group that did this sort of thing with regularity, a group that would expand beyond the three of them.

    On that night they created an association called Societe Poursuite, an homage to the Vidocq Society, a similarly themed group named after a nineteenth-century French detective named Eugene Francois Vidocq.

    Similar in some ways to the Vidocq Society, Societe Poursuite - which translated as Pursuit Society - now boasted more than three hundred and seventy members worldwide. And since its inception on that summer night in 1998, it had contributed to the solving of more than sixty homicides around the world.

    The group met every month in New York City, with their annual conclave held in a different major city on the east coast each October, rotating between New York, Philadelphia, and Washington D.C.

    This year their eleventh annual conclave would meet in Philadelphia, at the Le Jardin hotel. On the final night, an evening which would include a five-course meal prepared by the hotel's Michelin-starred chef Alain Cochel, there would be a speech by the Attorney General for the Commonwealth of Pennsylvania.

    Shepherd had been a homicide detective in Philadelphia for more than twenty years. When Jessica had come into the unit, it had been Kevin Byrne and John Shepherd who had showed her the ropes. While Byrne taught her - indeed, in many ways was still teaching her - how to work a crime scene, it was John Shepherd who taught her how to walk into an interrogation room, how to position her body at first so as not to intimidate, how to walk that gossamer-thin line between treating someone like a suspect and like a witness, how to coax that first lie out of their mouths, and then, an hour or two later, how to slam it back in their faces.

    The PPD had lost a great one when he retired.

    John Shepherd, turned out in a smart navy blue suit, opened his arms. 'Jess,' he said. 'Beautiful as ever.'

    They embraced. Even though they were still on the same side, they were no longer on the same team, and shows of affection were now allowed. 'We miss you, John.'

    Shepherd looked at Byrne. 'And if I wasn't head of security here, I'd have to call security on this shady-looking character.'

    The two men did the handshake, shoulder-bump, back-slap, I- swear-to-God-I'm-not-gay thing. Men, Jessica thought. God forbid they should show emotion in public. Cops were the worst.

    'You look good, Johnny,' Byrne said.

    'Underworked and overpaid.'

    Shepherd did look healthier than he ever had. Anytime you could get away from cop food and cop hours, you looked better. Tall and Denzel-handsome, now in his salt-and-pepper fifties, Shepherd looked relaxed, and in charge.

    He led them to the other side of the lobby, to the other side of a tall frosted-glass panel that somehow managed to keep the noise of arriving guests out of the tastefully appointed lounge.

    They stood at the far end of the bar, away from everyone. Without asking, three cups of coffee, with creamers on ice, were put in front of them.

    'So what are you up to?' Shepherd asked. 'Keeping the peace?'

    'Disturbing it whenever possible,' Byrne said. 'How are things here?'

    'Had a door pusher last month.'

    A door pusher was one of the more unsophisticated breeds of hotel criminal. He was a guy who got into the hotel, went to upper floors, and simply pushed on doors to find one that was unlocked, or improperly closed or, God help the room attendant, left open by housekeeping. These were guys who always had a record for B & E, generally nonviolent types but a real nuisance in hotel security work.

    'You take him down?' Byrne asked.

    'Guy hit the Sheraton Society Hill in March, moved over to the Hyatt Penn's Landing in May. We had him on tape, but he was slick - ball caps, glasses, packing his waist to look heavier. Wore a suit one time, sweats and sneaks the next. We got him, though.'

    They kicked the cop talk around for a while, until Shepherd moved his stool closer and lowered his voice. 'Now, I know how magnetic and incredibly charming I am, but I think y'all are here for another reason.'

    Byrne took a moment. 'There's a convention here. We think we might have a connection to a case we're working.'

    Shepherd nodded. 'The serial?'

    'Yeah.'

    'Lay it out.'

    Byrne told Shepherd the details.

    'And his name is George Archer?' Shepherd asked.

    'Yeah.'

    'Hang on.'

    Shepherd left the bar, returned a few minutes later. 'No one registered here under that name. Maybe he's staying somewhere else. Do you have a description on the guy?'

    'Not yet,' Byrne said. 'We have a request in to the state police. But they may not even have a picture. The guy was questioned, but he was never arrested or charged.'

    Shepherd nodded. He'd been right where Jessica and Byrne were.

    'Can you reach out to some of the other hotels, see if they have a George Archer?' Byrne asked.

    'No problem. I'll make a few calls.' Shepherd pointed to the other side of the lobby. 'They're setting up in the Crystal Room right now. It's going to be a big deal tonight, even bigger tomorrow.'

    'Do you have cameras in there?'

    John Shepherd chuckled. 'Is the pope .. . what is the pope now, by the way?'

    'German.'

    'Doesn't sound as good as Polish, does it?'

    'No.'

    'We have cameras,' Shepherd said. 'Come on.'

    Inside was a small outer office, which led, through another secure door, to a larger room in which two people were working.

    Shepherd spoke to a young woman at one of the desks, wrote something on the pad. While he was showing Jessica and Byrne the surveillance capabilities of the hotel, she would be putting in calls to the security directors of the surrounding hotels, looking for a guest named George Archer.

    Jessica scanned the monitors. The one on the right had six windows up that showed the huge atrium, viewed from the mezzanine level. A dozen people or so had congregated near the center of the room. A man and a woman, middle-aged, stood at the front desk. An elderly woman chatted with the concierge. A few seconds later the view shifted to the parking lot and front entrance. A limo idled at the front door as a pair of young bellmen pulled a number of large suitcases from the trunk. Another bellman leaned into the passenger window of a waiting cab.

    The software rotated the windows, floor after floor, with a view of the elevators constantly in the upper right-hand section of the screen.

    Shepherd sat down, clicked a few keys, and more than sixty small windows lined up on the two monitors. 'We've got two dome cams in every hall, clock cams in all the personnel spaces, half-zone weatherproof bullet cams in the parking lot, and four state-of-the-art 360-degree pan-and-tilt domes in the atrium and lobby, watching the desk and the money room. Not too much goes on here that we don't see.'

    'This is a real voyeur's delight,' Byrne said.

    'Wait until you see the bathroom cams,' Shepherd said, with a wink.

    Jessica and Byrne had done a lot of work with the Audio-Visual Unit of the PPD, as well as the communications unit, which monitored the PPD street cams, for which Philadelphia was getting more and more funding.

    Shepherd brought up the Crystal Room on a split screen. There was a man at the lectern, clearly an employee of whatever company was providing the PA and sound systems for the event. He performed a sound check.

    'So the people in this society used to be either cops or prosecutors?' Jessica asked.

    'Not at all,' Shepherd said. 'Some were in forensics, some worked for medical examiners' offices, some of them were never on the job at all. There are pretty tight membership rules and dues, which are kind of steep, so they keep out the lowlifes and the thrill seekers.'

    'There goes my shot at membership,' Byrne said.

    'Believe it.'

    'Are they any good at what they do?' Jessica asked.

    Shepherd nodded. 'That's my understanding. Every case they take on has to be formally presented to them by a bona fide agency. They don't work with the FBI or the NYPD, but just about everyone else of note has presented something.'

    The three of them watched the monitors for a while, the constant rotation of views from within and without the hotel. It was a relentless flow: staff, guests, visitors, deliveries.

    Was one of them their killer? Jessica wondered. Would she know him if she saw him?

    Jessica got onto the Société Poursuite website. In addition to a brief history, its mission statement, and an explanation of what the group was about, there were lists of its members, officers, past officers, and sub-chapters around the world. It was clear that the group chose its cases carefully, perhaps with an eye on choosing only those that had a chance of resolution.

    The menu at the bottom offered links to other sites and to message boards.

    'Check the message boards,' Byrne said. Jessica clicked over. There were a few dozen ongoing topics. One was a discussion of current trends in forensics. Another was a discussion of the disposition of homicide cases around the world. There was a discussion of ideas for cases for the group to tackle. This board had more than four thousand entries. Jessica clicked over, and as she scrolled through the posts her skin began to crawl.

    One by one the entries appeared. They were all there. All the original homicides had been suggested as cases in which the group might be interested. Melina Laskaris, Marcellus Palmer, Antoinette Chan, Margaret Van Tassel. And they were all suggested by one user. The user name was cssl835.

    Jessica got on the phone to John Shepherd, asking him to talk to someone from the group about the criteria for posting. A few minutes later, Shepherd called back.

    'I talked to the president of the group,' Shepherd said. 'He says you don't have to log in or be a member to post something on that board. He says that it would discourage people from coming forward.'

    'So they have no record of who this "cssl835" might be?'

    'No,' Shepherd said. 'Sorry.'

    Jessica thanked him, hung up. She looked back at the screen. Whoever was doing this was connected to, or had an interest in, Société Poursuite. Was it George Archer? Was George Archer css1835?

    Jessica looked at the material she had received from Frederic Duchesne.

    Camille Saint-Saens - css - had been born in 1835.

    Byrne turned to look at her. 'Yeah?'

    'Could I see you for a minute?'

    Byrne crossed the room, dropped his weapon in his file drawer, and walked into Dana Westbrook's office.