The Square Root of Murder (Professor Sophie Knowles)

tell who was saying what.
    Pam and Liz each held one of Casey’s hands. All were in tears when the next round began.
    “He was already dead.”
    “I wanted to just leave.” This, I was sure, was from Casey.
    “We went there to help Casey try to negotiate.”
    “We started to knock, but the door just pushed open.”
    “I didn’t want to go through with it.” Casey again.
    “I’ve been a wreck.” And again.
    “It was a stupid thing to do, but he was dead. And there was his computer screen—”
    “With all our grades.”
    Eventually, the girls started from the beginning, when they’d headed up to the fourth floor around two thirty on Friday. They took turns describing the crime scene, with their professor on the floor behind his desk. It was like hearing Rachel all over again and I realized they didn’t match the profile of a killer any more than Rachel did. Assuming I’d know one when I saw one.
    “We really are disgusted with ourselves,” Liz said.
    “You should be,” I said. “But I’m glad you’re telling the truth now.”
    “What should we do?” Pam asked, surprising me. I’d have expected her to exact a promise from me to not breathe a word.
    “You should go to the police,” I said, all virtuous.
    “Aren’t you working with the cops?” Liz asked.
    Uh-oh. Virtue was about to fly out the open window next to our table.
    “Yes, I am,” I said, mentally reserving the fact that the cops didn’t know it. “And I have a couple of questions if you don’t mind—”
    “Oh, my God. Can we help?” Casey said, while Liz and Pam gave me an “anything you like” look.
    I took a notebook out of my purse, as befitted one helping out the Henley PD.
    “Let’s start with your arriving at Dr. Appleton’s office, about two thirty you said?”
    “Uh-huh. After the party. His car was still on campus, so we knew he was in and we thought if we all went up together we might be able to make him see reason.”
    An intimidating group, but I doubted Keith would have been fazed by three of his students. I envisioned his standing up behind his desk and flicking them out the door.
    “You all stayed to help me clean up, so it was after that?”
    “We wanted to make sure you were gone,” Casey said.
    Pam shot her a look. The old Pam was back. “We didn’t want anyone interrupting us,” she said.
    I got it.
    “About Dr. Appleton’s office. I know it won’t be pleasant, but if you can go back in your minds and tell me if you saw anything out of the ordinary?”
    The girls closed their eyes, séance style, and at that moment I felt they were putty in my hands. I wasn’t proud of the rush I got. Was this how Archie felt when I was cowering before him yesterday afternoon? If I didn’t get my promotion, was I too old to sign up for the police academy? Questions for another time.
    “It was a mess,” Pam said. “And, you know, Dr. Appleton always kept everything in order.”
    “A real neat freak,” Liz said.
    “Was there any food around?”
    The girls looked at each other and nodded.
    “There was a paper plate with cake outside the door,” Pam said. “I think I saw Rachel make up a plate for him.”
    “And a can of soda,” Liz said. “Some kind of cola, I think.”
    “We were going to pick it up and take it in, but we decided not to move it, in case that’s where he wanted it,” Casey said.
    “You know, like, maybe he was trashing it,” Liz added.
    I tried to process this factoid and insert it into my mental timeline. Rachel took the cake upstairs and left it outside Keith’s door at about one forty-five. The girls saw it there at two thirty, but Woody saw it on the chair in Keith’s office at four. And, of course, the police didn’t see it all because Woody tossed it to protect Keith’s reputation as a neat freak.
    I was already juggling all the visitors to Keith’s postmurder office. The killer was there before Rachel and the girls arrived, but someone else was there between the girls’ visit and Woody’s discovery. It had to have been the killer coming back to plant evidence against Rachel. Would a killer risk two trips? I wondered if all crime scenes were as busy as this one.
    It was clear that I was going to need to create a real, physical timeline. I wished I’d brought my laptop to the library, but there’d be time once I got to my home office.
    “I know things were broken and on the floor, but was there any extra paper? I’m wondering about that yellow paper you all