THE DIGITAL CLOCK on the microwave read 7:08. I was physically wrung out and mentally fried after combing the Tenderloin all day, coming up with nothing more than a list of all the places where Alfred Brinkley didn't live.

I wasn't just frustrated, either. I felt dread. Fred Brinkley was still out there.

I put a Healthy Choice macaroni and cheese into the microwave, pressed the minute button five times.

As my dinner revolved, I ran the day through my mind again, searching for anything we might have overlooked in our tour of six dozen sleazy hotels, the interviews with useless desk clerks and scores of low-rent tenants.

Martha brushed up against me, and I stroked her ears, poured dog chow into a bowl. She lowered her head, wagged her plumey tail.

"You're a good girl," I said. "Light of my life."

I had just cracked open a beer when my doorbell rang.

What now?

I limped to the window to see who had the audacity to ring my bell – but I didn't know the man staring up at me from the sidewalk.

He was clean shaven, half in shadow – holding up an envelope.

"What do you want?"

"I have something for you, Lieutenant. It's urgent. I have to deliver this to you personally."

What was he? A process server? A tipster? Behind me, the microwave beeped, alerting me that dinner was ready.

"Leave it in the mailbox!" I shouted down.

"I could do that," said my visitor. "But you said on TV, 'Do you know this man?' Remember?"

"Do you know him?" I called.

"I am him. I'm the one who did it."

I HAD AN INSTANT of stunned confusion.

The ferry shooter was at my door?

Then I snapped to.

"I'll be right there!" I shouted down.

I grabbed my gun and holster from the back of a chair, clipped my cuffs to my belt. As I rounded the second-floor landing, I called Jacobi on my cell phone, knowing full well that I couldn't wait for him to arrive.

I could be walking into a shooting gallery, but if the man downstairs was Alfred Brinkley, I couldn't chance letting him get away.

My Glock was in my hand as I cracked the front door a couple of inches, using it as a blind.

"Keep your hands where I can see them," I called out.

The man looked volatile. He seemed to hesitate, move back into the street, then forward toward my doorway. His eyes darted everywhere, and I could make out that he was singing under his breath.

God, he was crazy – and he was dangerous. Where was his gun?

"Hands up. Stay where you are!" I yelled again.

The man stopped walking around. He raised his hands, flapping his envelope side to side like a white flag.

I scanned his face, trying to match what I saw against my mental picture of the shooter. This guy had shaved, and he'd done a poor job of it. Wisps of beard showed dark against his pale skin.

In every other way, I saw a match. He was tall, skinny, wearing clothes similar or identical to those worn by the shooter about sixty hours ago.

Was this Alfred Brinkley? Had a violent killer simply rung my doorbell to turn himself in? Or was this a different kind of lunatic, looking for a spotlight?

I stepped out onto the moon-shadowed sidewalk, gripping my Glock in both hands, pointing at the man's chest. The unwashed smell of him wafted toward me.

"It's me," he said, staring down at his shoes. "You said you're looking for me. I saw you on TV. In the video store."

"Get on the ground," I barked at him. "Facedown, with your fingers entwined on top of your head where I can see them."

He swayed on his feet. I shouted, "Get down – do it now!" and he dropped to the sidewalk and placed his hands on his head.

With my gun pressed to the back of his skull, I ran my hands over the suspect's body, checking for weapons, images from Rooney's video flickering through my mind the whole time.

I pulled a gun from his jacket pocket, stuck it into the back of my waistband, and searched for more weapons. There were none.

I holstered my Glock and yanked the cuffs from my belt.

"What's your name?" I asked, dragging back each stick-thin arm until the cuffs snapped around his wrists. Then I picked the envelope up from the sidewalk and stuffed it into my front pocket.

"Fred Brinkley," he said, his voice filling with agitation. "You know me. You said to come in, remember? 'We will find whoever did this terrible thing.' I wrote it all down."

The pictures from the Rooney video looped in my head. I saw this man shoot five people. I saw him shoot Claire.

I took his wallet from his hip pocket with a shaking hand, flipped it open, saw his driver's license by the dim light of the streetlamp across the road.

It was Alfred Brinkley.

I had him.

I read Brinkley his rights and he waived them, saying again, "I did it. I'm the ferry shooter."

"How did you find me?" I asked.

"Your address is on the Internet. At the library," Brinkley told me. "Lock me up, okay? I think I could do it again."

Jacobi's car pulled up just then, brakes squealing. He bolted out of the driver's seat with his gun in hand.

"You couldn't wait for me, Boxer?"

"Mr. Brinkley is cooperating, Jacobi. Everything is under control."

But seeing Jacobi, knowing that the danger was over, sent waves of relief through me, making me want to laugh and cry and shout woo-hoooo all at the same time.

"Nice work," I heard Jacobi say. I felt his hand on my shoulder. I gulped air, trying to calm myself as Jacobi and I got Brinkley to his feet.

As we folded him into the backseat of Jacobi's car, Brinkley turned toward me.

"Thank you, Lieutenant," he said, his crazy eyes still darting, his face crumpling as he broke into tears. "I knew you would help me."

JACOBI FOLLOWED ME into my office, our nerves strung so tight we could have played them like guitars. As we waited for Brinkley to be processed, we hunched over my desk, drinking coffee, talking over what we needed to do next.

Brinkley had confessed to being the ferry shooter, and he'd refused counsel. But the written statement he'd given me was a rambling screed of nonsense about white light, and rat people, and a gun named "Bucky."

We had to get Brinkley's confession on the record, show that while Alfred Brinkley might be mentally disturbed, he was rational now.

After I called Tracchio, I phoned Cindy, who was not only my good friend but top dog on the Chronicle's crime desk, to give her a heads-up on Brinkley's capture. Then I paced around the squad room, watching the hands of the clock crawl around the dial as we waited for Tracchio to arrive.

By 9:15 Alfred Brinkley had been printed and photographed, his clothes swapped out for a prison jumpsuit so that his garments could be tested for blood spatter and gunshot residue.

I asked Brinkley to let a medical tech take his blood, and I told him why: "I want to make sure you're not under the influence of alcohol or drugs when we take your confession."

"I'm clean," Brinkley told me, rolling up his sleeve.

Now Brinkley waited for us in Interview Room Number Two, the box with the overhead video camera that worked most of the time.

Jacobi and I joined Brinkley in the gray-tiled room, pulling out the chairs around the scratched metal table, taking our seats across from the killer.

My skin still crawled when I looked at his pale and scruffy face.

Remembered what he'd said.

"I'm the one who did it."