"I wouldn't rule out a stranger," I said. "If the person is very smooth, she may have trusted him, let him in for some other reason."

"At that hour?"

His eyes flicked me as they went around the room. "What? He's selling magazine subscriptions, Good Humor bars at ten o'clock at night?"

I didn't reply. I didn't know.

We stopped at the open doorway leading into a hallway.

"This is the first blood," Marino said, looking at the dried spatters on the wall. "She got cut right here, the first cut.

I figure she's running like hell and he's slashing."

I envisioned the cuts on Beryl's face, arms, and hands.

"My guess," he went on, "is he cut her left arm or back or face at this point. The blood on the wall here's cast off from blood slinging off the blade. He'd already cut her at least once, the blade was bloody, and when he swung again drops flew off and hit the wall."

The stains were elliptical, about six millimeters in diameter, and became increasingly elongated the farther they arched left of the doorframe. The spread of drops spanned at least ten feet. The assailant had been swinging with the vigor of a hard-hitting squash player. I felt the emotion of the crime. It wasn't anger. It was worse than that. Why did she let him in!

"Based on the location of this spatter, I'm thinking the drone was right about here," Marino said, positioning himself several yards back from the doorway and slightly to the left of it. "He swings, cuts her again, and as the blade follows through, blood flies off and hits the wall. The pattern, as you can see, starts here."