I WAS PERSPIRING HEAVILY AND FELT WEAK ALL OVER, BUT I MANAGED to drive. Bonehead move, Brennan. Microbes win this one. Reduce your speed. You don’t want to be stopped. Get home. Find it. There’s got to be something.

I flew along Sherbrooke, circled the block, and shot down the drive. The garage door was beeping again. Damn. Why can’t Winston fix that? I parked the car and hurried to my apartment. Check the dates.

A satchel rested on the floor outside my door.

“Shit. Now what?”

I looked down at the backpack. Black leather. Made by Coach. Expensive. A gift from Max Ferranti. A gift to Katy. It was lying outside my door.

My heart froze in my chest.

Katy!

I opened the door and called her name. No answer. I punched in the security code and tried again. Silence.

I raced from room to room, searching for signs of my daughter, knowing I would find none. Did she remember to bring her key? If she had, she wouldn’t have left her pack in the hall. She had been here, found me not home, left her pack, and gone somewhere.

I stood in the bedroom, trembling, a victim of virus and fear. Think, Brennan. Think! I tried. It wasn’t easy.

She arrived and couldn’t get in. She’s gone for coffee, or window shopping, or to look for a phone. She’ll call in a few minutes.

But if she didn’t have the key, how did she get through the outer door into the corridor to my unit door? The garage. She must have come through the pedestrian door into the garage, the one that’s not latching as it closes.

The phone!

I ran to the living room. No message. Could it be Tanguay? Did he have her?

That’s impossible. He’s in jail.

The teacher is in jail. But he’s not the one. The teacher isn’t the one. Or is he? Did he keep the Rue Berger room? Did he bury the glove with Katy’s picture in Gabby’s grave?

The fear sent a wave of nausea rising up my esophagus. I swallowed and my swollen throat screamed in protest.

Check the facts, Brennan. They may have been holidays.

I booted the computer with shaking hands, my fingers barely able to work the keys. The spreadsheet filled the screen. Dates. Times.

Francine Morisette-Champoux was killed in January. She died between 10 A.M. and noon. It was a Thursday.

Isabelle Gagnon disappeared in April, between 1 and 4 P.M. It was a Friday.

Chantale Trottier disappeared on an afternoon in October. She was last seen at her school in Centre-ville, miles from the west island.

They died or disappeared during the week. During the day. The school day. Trottier may have been abducted after school hours. The other two were not.

I grabbed the phone.

Ryan was out.

I slammed the receiver. My head felt like lead and my thoughts were coming in slow motion.

I tried another number.

“Claudel.”

“Monsieur Claudel, this is Dr. Brennan.”

He didn’t answer.

“Where is St. Isidor’s?”

He hesitated, and I didn’t think he was going to answer.

“Beaconsfield.”

“That’s what, about thirty minutes from downtown?”

“Without traffic.”

“Do you know what the school hours are?”

“What’s this about?”

“Can I just have an answer?” I was pushing the envelope and about to crack. My voice must have told him.

“I can ask.”

“Also, find out if Tanguay ever missed any days, if he called in sick or took personal leave, particularly on the days Morisette-Champoux and Gagnon were killed. They’ll have a record. They’d have needed a substitute unless school was not in session for some reason.”

“I’m going out there tom—”

“Now. I need it now!” I was poised on the edge of hysteria, toes clutching the end of the board. Don’t make me jump.

I could hear his face muscles harden. Go ahead, Claudel. Hang up. I’ll have your ass.

“I’ll get back to you.”

I sat on the edge of the bed, staring numbly at dust playing tag in a shaft of sunlight.

Move.

I went to the bathroom and splashed cold water on my face. Then I fished a plastic square from my briefcase and returned to the computer. The case was labeled with the Rue Berger address and the date 94/06/24. I raised the lid, removed a CD-ROM disk, and set it in the drive.

I opened a program for image viewing, bringing up a row of icons. I chose Album then Open, and a single album name appeared in the window. Berger.abm. I double-clicked and three rows of pictures filled the screen, each displaying six still photos of St. Jacques’s apartment. A line at the bottom told me the album contained a hundred and twenty shots.

I clicked to maximize the first image. Rue Berger. The second and third showed the street from different angles. Next, the apartment building, front and back. Then the corridor leading to the St. Jacques apartment. Views of the apartment’s interior started with image twelve.

I moved through the pictures, scrutinizing every detail. My head pounded. My shoulder and back muscles were like high-tension wires. I was back there again. The suffocating heat. The fear. The odors of filth and corruption.

Image by image I searched. For what? I wasn’t sure. It was all there. The Hustler centerfolds. The newspapers. The city map. The staircase landing. The filthy toilet. The greasy countertop. The Burger King cup. The bowl of SpaghettiOs.

I stopped, stared at the still life. File 102. A grimy plastic bowl. Fatty white rings congealing in red sludge. A fly, front legs clasped as if in prayer. An orange boulder rising from the sauce and pasta.

I squinted, leaned in. Could I be seeing what I thought I was seeing? There. Coursing across the orange chunk. My heart pounded. It couldn’t be. We couldn’t be that lucky.

I double-clicked, and a dotted line appeared. I dragged the cursor, and the line became a rectangle, its borders a string of rotating dots. I positioned the rectangle directly over the orange blob and zoomed in, magnifying the image again and again. Double. Triple. Up to eight times its actual size. I watched as the faint parabola I had spotted became an arched trail of dots and dashes.

I zoomed out and examined the entire arc.

“Oh, Jesus.”

Using the image editor, I manipulated the brightness and contrast, modified the hue and saturation. I tried reversing the color, changing each pixel to its complement. I used a command to emphasize edges, sharpening the tiny trail against the orange background.

I leaned back and stared. It is. I inhaled deeply. Sweet Jesus, it really is.

With a trembling hand I reached for the phone.

A recorded message told me Bergeron was still on vacation. I was on my own.

I sifted the possibilities. I’d seen him do it several times. I could try. I had to know.

I looked up another number.

“Centre de Détention Parthenais.”

“This is Tempe Brennan. Is Andrew Ryan there? He’d be with a prisoner named Tanguay.”

“Un instant. Gardez la ligne.”

Voices in the background. Come on. Come on.

“Il n’est pas ici.”

Damn. I looked at my watch. “Is Jean Bertrand there?”

“Oui. Un instant.”

More voices. Clatter.

“Bertrand.”

I identified myself, explained what I’d found.

“No shit. What did Bergeron say?”

“He’s on vacation until next Monday.”

“Cheese, that’s beautiful. Kind of like your false starts, eh? What do you want me to do?”

“Find a piece of plain Styrofoam and get Tanguay to bite down on it. Don’t stick it too far into his mouth. I just need the front six teeth. Have him bite edge to edge so you get nice clean tooth marks, one arch on each side of the plate. Then I want you to take the Styrofoam downstairs to Marc Dallair in photography. He’s way in back, behind ballistics. You got that?”

“Yeah. Yeah. How do I get Tanguay to agree to this?”

“That’s your problem. Figure something out. If he’s screaming innocent he should be delighted. “

“Where am I supposed to come up with Styrofoam at four-forty in the afternoon?”

“Go buy yourself a bloody Big Mac, Bertrand. I don’t know. Just get it. I’ve got to catch Dallair before he leaves. Get moving!”

Dallair was waiting for an elevator when my call came. He took it at the reception desk.

“I need a favor.”

“Oui.”

“Within the hour Jean Bertrand will bring bite mark specimens to your office. I need to have the image scanned into a Tif file and sent to me electronically as soon as possible. Can you do that?”

There was a long pause. In my mind I could see him glance at the elevator clock.

“Does this have to do with Tanguay?”

“Yes.”

“Sure. I’ll wait.”

“Angle the light across the Styrofoam as close to parallel as possible to really bring the marks out. And be sure to include a scale, a ruler or something. And please make sure the image is exactly one to one.”

“No problem. I think I have an ABFO ruler here somewhere.”

“Perfect.” I gave him my e-mail address and asked him to call when he’d sent the file.

Then I waited. Seconds crept by with glacial slowness. No phone. No Katy. The digits on the clock glowed green. I heard them change. Click, click, click as the rotors turned.

When the phone rang I grabbed it.

“Dallair.”

“Yes.” I swallowed and the pain was excruciating.

“I sent the file about five minutes ago. It’s called Tang.tif. It’s compressed, so you’ll have to unencode. I’ll stick here until you’ve downloaded, to be sure there’s no problem. Just send a reply. And good luck.”

I thanked him and hung up. Moving to the computer I logged into my mailbox at McGill. The Mail Waiting!!! message glowed brightly. Ignoring other unread mail, I downloaded the file Dallair had sent, and returned it to its graphic format. A dental imprint arched across the screen, each tooth clearly visible against a white background. To the left and below the impression was a right-angle ABFO ruler. I sent Dallair a reply and logged off.

Back in the imaging program, I called up Tang.tif and double-clicked it open. Tanguay’s impression filled the screen. I retrieved the bite mark in the Rue Berger cheese, and tiled the two images side by side.

Next I converted both images to an RGB scale, to maximize the amount of information in the pictures. I adjusted tone, brightness, contrast, and saturation. Finally, using the image editor I sharpened the edges on the Styrofoam impression as I had with the indentations in the cheese.

For the type of comparison I planned to try, both images had to be to the same scale. I got out a needle point caliper and checked the ruler in the Tanguay photo. The distance between hash marks was exactly one millimeter. Good. The image was one to one.

There was no ruler in the Berger photo. Now what?

Use something else. Go back to the full image. There has to be a known.

There was. The Burger King cup touched the bowl adjacent to the cheese, its red and yellow logo clear and recognizable. Perfect.

I ran to the kitchen. Let it still be here! Throwing open the cabinet doors, I rummaged through the trash under the sink.

Yes! I washed off the coffee grounds and carried the cup to the computer. My hands trembled as I spread the calipers. The upright arm of the logo B measured exactly 4 millimeters across.

Selecting the resize function in the image editor I clicked on one edge of the B on the Rue Berger cup, dragged the cursor to the far border, and clicked again. Having chosen my calibration points I told the program to resize the entire image so that the B measured exactly 4 millimeters across at that position. Instantly the picture changed dimension.

Both images were now one to one. I looked at them side by side on the computer screen. The impression Tanguay had given showed a complete dental arch, with eight teeth on each side of the midline.

Only five teeth had registered in the cheese. Bertrand was right. It was like a false start. The teeth had gripped, slid, or been retracted, then bitten a chunk from behind the mark I was now seeing.

I stared at the trail of indentations. I was sure it was an upper arch. I could see two long depressions to either side of the midline, probably the central incisors. Lateral to them were two similarly oriented but slightly shorter grooves. Farther out, on the left of the arcade, was a small, circular dent, probably made by the canine. No other teeth had registered.

I ran my sweaty palms down the sides of my shirt, arched my back, and took a deep breath.

Okay. Position.

Choosing the Effect function, I clicked on Rotate, and slowly maneuvered Tanguay’s dental impression, hoping to achieve the same orientation as the mark in the cheese. Click by click I rotated the central incisors clockwise. Forward, then backward, then forward again, a few degrees at a time, my anxiousness and clumsiness prolonging the process. It took an entire growing season, but at last I was satisfied. Tanguay’s front teeth lay at the same angle and position as their counterparts in the cheese.

Back to the Edit menu. Stitch function. I selected the cheese as the active image and the Tanguay impression as the floating image. I set the the transparency level at 30 percent, and Tanguay’s bite mark grew cloudy.

I clicked on a spot directly between Tanguay’s front teeth, and again on the corresponding gap in the cheese arcade, defining a stitch point on each image. Satisfied, I activated the Place function, and the image editor superimposed Tanguay’s bite mark directly over that in the cheese. Too opaque. The cheese trail was completely obliterated.

I raised the transparency level to 75 percent, and watched the Styrofoam dots and dashes fade to ghostly transparency. I now had a clear view of the dents and hollows in the cheese through the impression made by Tanguay.

Dear God.

I knew instantly the bites were not by the same person. No amount of manual manipulation or fine tuning of the images could alter that impression. The mouth that had bitten into the Styrofoam had not left the marks in the cheese.

Tanguay’s dental arch was too narrow, the curve at the front much tighter than that preserved in the cheese. The composite image showed a horseshoe overlying a partial semicircle.

More striking, the person eating cheese at the Rue Berger flat had an irregular break to the right of the normal midline gap, and the adjacent tooth shot off at a thirty-degree angle, making the tooth row look like a picket fence. The cheese eater had a badly chipped central incisor, and a sharply rotated lateral.

Tanguay’s teeth were even and uninterrupted. His bite showed neither of these traits. He had not bitten that cheese. Either Tanguay had entertained a guest at Rue Berger, or the Rue Berger apartment had nothing to do with Tanguay at all.