AT FIRST, IT WAS A BLUR-someone standing in front of the camera. When he stepped back, we saw that it was the same man, only now dressed in plain green coveralls and a black baseball cap that said MO.

The scene was obviously Tess Olsen’s living room. Today. Mrs. Olsen was in the background on all fours, naked and visibly trembling. Her mouth was taped shut. And around her neck was the red dog leash.

He had filmed everything, playing to an audience the whole time he was here.

The feeling in the den went from bad to a lot worse. The killer-or the terrorist, as I’d already begun to think of him-approached Tess Olsen. He pulled hard on the leash, and she struggled to her feet. The woman was sobbing uncontrollably. Possibly she knew what was going to happen now. Did that mean she knew the killer? How would she know him? Because of a book she was writing? What was her latest project?

Seconds later, the man had pulled her out on the terrace. He first peeled, then ripped the tape off her mouth. We couldn’t hear much from this distance-not until he grabbed Mrs. Olsen and hung her over the edge. Then her piercing screams reached the camera’s microphone, which was set up maybe twenty feet away.

All the while, the killer kept checking over his shoulder, looking toward the camera every few seconds.

“See that? How he moved back into the frame?” Bree said. “He wasn’t just putting on a show for the crowd on the street. This was meant for us as well-for whoever found the tape, anyway. Look at the bastard’s face.” Now he was smiling. Even from this distance, his eerie grin was clear and unmistakable.

The next few seconds seemed to stretch on forever, as I’m sure they did for Tess Olsen. He pulled her back inside and then set her down on the floor. Did she think there would be a reprieve? That she was to be spared? Her shoulders heaved once, then she began to cry again. A minute or so later, he brought her out on the terrace again.

“Here it comes,” Bree said gravely. “I don’t want to watch this.” But she did. We all did.

The killer was a powerful man, probably over six feet tall and well built. He shocked me by lifting Tess Olsen like a barbell, straight up over his head. He looked back at the camera one more time-Yes, you bastard, we’re watching-then winked and threw her off the balcony.

“My God,” Bree whispered. “Did he just wink at us?”

He didn’t leave the terrace, though. Or the picture frame. I could see by the angle of his head that he wasn’t looking straight down to where she fell. He was looking out at his audience, at the people down on the street. He was taking chances that he didn’t need to take.

In the scheme of things, that was good for us. Maybe that’s how we’d find him, catch this bastard. Because he was reckless-and liked to preen in front of an audience.

Then I analyzed my own thought: We, not they, were going to get this sonofabitch.

And then, the killer spoke to the camera, and this was the eeriest part of all. “You can try to capture me,” he said, “but you will fail… Dr. Cross.”

Sampson, Bree, and I turned to one another. John and I were speechless, and all Bree could manage was “Holy shit, Alex.”

Ready or not, I was back in the game.

WELL, I WASN’T READY. Not yet, anyway. Four days after the Riverwalk murder, I was thinking about my patients. I was already conflicted, though. I was trying not to focus on Tess Olsen’s murder, and who the maniac killer might be, and how he could possibly know me, and what the hell he wanted from me.

I couldn’t help starting my day by checking the latest news on washingtonpost.com. Nothing further had happened during the night, thank God. No more murders, so at least he wasn’t on a spree.

The morning’s sessions would keep me on my toes, anyway. It was my biggest day of the week, the one I looked forward to but also dreaded in some ways. There was always the hope that I might do somebody some good, have a breakthrough. Or, possibly, I could fall right on my ass.

It started at seven with a recently widowed DC firefighter who was in conflict between a sense of duty to his job and kids, and a growing sense of meaninglessness about life that produced daily thoughts of suicide.

At eight I saw a Desert Storm vet who was still wrestling with demons he’d brought home from the war. He was a referral from my own therapist, Adele Finally, and I was hopeful that I could help him eventually. Still, this was the crisis stage of his treatment, so it was too early to tell if we were really communicating.

Next came a woman whose postpartum depression had left her with a lot of ambivalence toward her six-month-old daughter. We discussed her little girl and even talked about my feelings-just for a minute-about Damon possibly heading off to prep school. Same as in police work, I was usually unorthodox in the sessions. I was there to talk to people, and I talked freely, for the most part.

I had a half-hour break, during which I checked in with Bree, then glanced at the news on washingtonpost.com again. Still nothing new, no further attacks, no explanations for the death of Tess Olsen.

The morning’s final patient was a Georgetown law student whose mysophobia had become so intense, she’d begun incinerating her own underwear every night.

Quite a morning. Satisfying in a strange way. And relatively safe-at least for me.

BREE CALLED THE OFFICE while I was eating an unbuttered hard roll before my one o’clock. “We did some close-up work on the tapes,” she said. “Tell me what you think of this, Alex. There’s a scar on the killer’s forehead. Shape of a half-moon. It’s fairly pronounced.”

I thought for a moment before answering. “Could mean head trauma at some time. This is a shot in the dark, but he could have damaged frontal lobes. People with frontal-lobe damage can display bad tempers and impulsiveness.”

“Thanks, Doc,” Bree said. “Nice having you on the team.”

I was on the team? Since when? Had I agreed to that? I didn’t think so.

After lunch, and the very nice homicide-case chat with Bree, I had my last client of the day, also my favorite, a woman in her midthirties named Sandy Quinlan.

Sandy was a recent transplant to DC from small-town life in northern Michigan, not far from Canada. She’d accepted an inner-city teaching job in Southeast, which had endeared her to me immediately.

Unfortunately, Sandy didn’t like herself very much. “I’ll bet you have a dozen clients like me. All these lonely, depressed single women in the big, bad city.”

“Actually, I don’t.” I told her the truth, a terrible habit with me. “You’re my only DSW in the BBC.”

Sandy got the joke and smiled, then went on. “Well, it’s just… pathetic. Nearly every woman I know is looking for the same dumb-ass thing.”

“Happiness?” I asked.

“I was going to say a man. Or a woman, I suppose. Somebody to love.”

I definitely saw a different person in Sandy than she saw in herself. She chose to appear as the classic loner stereotype, nice looks hidden behind black-rimmed glasses and dark, baggy clothes. As she’d grown comfortable with me, she’d proven to be personable, interesting, and funny when she wanted to be. And she cared deeply about the children she taught. She talked about them frequently and in the warmest terms. No ambivalence whatsoever.

“I have a real hard time seeing you as pathetic,” I finally said to her. “Sorry, it’s just an opinion. I could be all wrong about that.”

“Well, when your therapist is probably your best friend, call it what you want.” Before I could respond, she laughed self-consciously. “Don’t worry, I don’t mean that as psycho as it sounds. I just mean that…”