Charlie documented the contents of the shelves with the camera. “These cleaners are industrial grade. They’re probably thirty percent bleach.”

Will recognized the Windex label on one of the spray bottles. He had the same cleaner at home. It contained vinegar to help cut the grease. “You can’t mix vinegar and bleach, right?”

“Right. It forms a chlorine gas.” Charlie followed Will’s gaze to the spray bottle. He laughed as he made the connection. “I’ll be right back.”

Will let out a deep breath that he felt like he’d been holding for the last two days. Bleach glowed just as brightly as blood when sprayed with Luminol, obscuring any evidence. Vinegar, by contrast, formed a natural bond with iron, making it more visible when it was sprayed. That explained why the spots in the hall glowed with such intensity. The killer had used the Windex to clean up the floor. He might as well have drawn an arrow to the bloodstains.

Charlie was back with Doug and another assistant. They worked in tandem, taking photographs and handing Charlie the brush and powder to check the Windex bottle for fingerprints. Charlie was methodical, starting from the top down, going from one side of the bottle to the other. Will had expected him to find fingerprints immediately. The bottle was half full. The janitorial staff must have used it. The closet wasn’t locked. The students would have access.

“It was wiped down,” Will guessed. The trigger and the area around the grip were clean.

“Don’t give up on me yet,” Charlie mumbled. The brush swept back and forth across the label. All of them knelt down as Charlie dusted the bottom surface.

“Bingo,” Will whispered. He could see a partial fingerprint on the bottom of the bottle. The black practically glowed against the dark blue liquid.

“What do you see?” Charlie asked. He took a flashlight out of his pocket and shone it on the clear plastic. “Holy Christ. Good catch, eagle eye.” He traded the flashlight for a piece of clear tape. “It’s a partial, probably the pinky finger.” He sat back on his heels so he could transfer the tape to a white card.

Will said, “His gloves would’ve been bloody. He had to take them off to clean the floor.”

Charlie stood up with Doug’s help. “We’ll drive this to the lab right now. I can wake some people up. It’ll take time, but it’s a good print, Will. This is a solid lead.” He told his assistant, “The other evidence is in the van. There’s a pill bottle in my tackle kit. Grab that, too.”

Will had forgotten about the bottle in Tommy Braham’s cabinet. “Did you field-test the capsules?”

“I did.” Charlie started down the hall toward the stairs. The black lights bounced off their white Tyvek suits. “It’s not coke, meth, speed, or any of the usual suspects. Was the kid into sports?”

“I don’t think so.”

“It could be a steroid or a performance enhancer. A lot of younger guys are using those to bulk up now. The Internet makes them easy to get. I sent some photos back to Central to see if they recognize the label or capsules. A lot of these dealers are into branding. They keep their labels consistent so their product gets advertised.”

Tommy didn’t strike Will as interested in weight lifting, but he’d been a skinny kid. Maybe he wasn’t happy with that. “Did you find any fingerprints on the bottle?”

Charlie stopped at his tackle box. He pulled out the pill bottle, which had been sealed in a proper evidence bag instead of the Ziploc Will had found in the kitchen. “I lifted two sets. The first was adult, probably male. The second was a partial webbing.” He indicated the skin between his thumb and index finger. “I don’t know if it’s male or female, but I’d guess whoever wrote those words on the label held it in her hands while she did. I’m saying ‘her’ because it looks like a woman’s handwriting.”

“Can I keep the bottle? I want to show it around and see if anybody recognizes it.”

“I already have some of the capsules in the van.” Charlie gave him the bag as they walked down the stairs. “You still want a lift to the Braham house? I think I can spare one of my guys to process the garage now.”

“That’d be great.” Will had forgotten his Porsche was still at the Taylor Drive house. He checked the time on his phone. Knowing it was already past ten o’clock made Will feel even more exhausted than he had before. He thought about Cathy Linton’s dinner invitation and his stomach rumbled.

Downstairs, Marty was awake by the door. He was talking to a large man who was his exact opposite except in skin color.

“You Agent Trent?” The man slowly made his way over. He was built like a linebacker who’d gone to seed. “Demetrius Alder.”

Will was too busy unzipping his clean suit to shake the man’s hand. “Thank you for cooperating with us today, Mr. Alder. I’m sorry we’ve kept you out so late.”

“I gave Lena all the tapes. I hope she comes up with something.”

Will assumed he would have heard from her hours ago if Lena had found anything of note in the security footage. Still, he told Demetrius, “I’m sure they’ll prove useful.”

“The dean wanted me to give you his number.” He handed Will a card. “He had me check all the buildings. We didn’t find anything else. All the dorms are empty. Somebody’s coming to fix the cameras first thing after the holiday.”

Will sat down so he could pull off the rest of the suit. He remembered something Marty had said earlier. “What about the car that was hit by the security camera?”

“It was parked in the loading dock. Good thing it was empty. Camera busted straight through the hatchback window.”

“Hatchback?” Will stopped worrying about the suit. “What kind of car was it?”

“I think it was one’a them old Dodge Daytonas.”

THE RAIN HAD TURNED into a light sleet by the time Charlie’s van reached the tow yard. Gusts of wind shook the vehicle. Water pooled in the parking lot. There was no way to get to the front door without getting soaked. Will felt his socks getting wet again. The blister on his heel was so raw that he was starting to limp.

“Earnshaw’s,” Charlie said, and Will guessed he meant the sign glowing over the building. There was a whippet-thin older man standing in the doorway dressed in bib overalls and a baseball cap. He held the door open for them as they ran into the building.

“Al Earnshaw.” The man offered his hand to both of them. He told Will, “You’re Sara’s friend, right? My sister’s told me a lot about you.”

Will guessed that explained the man’s uncanny resemblance to Cathy Linton. “She’s been very kind to me.”

“Sure she has.” Al bellowed a good-natured laugh, but he slapped Will on the arm hard enough to throw off his balance. “Car’s in the back.” He motioned them toward the door behind the counter.

The shop was large, with the usual array of girlie calendars and posters of sexy, bikini-clad ladies washing cars. There were six lifts, three on each side. The tool chests were neatly lined up, their covers locked down tight. Al had turned on the propane heaters, but the cold was still biting. The roll-up doors in the back rattled from the wind. Allison’s Dodge Daytona was on the ground by the last lift. The back windshield was buckled in the center, just as Demetrius had said.