Good catch…

They also found a well-thumbed book, sprouting Post-it notes.

A Comprehensive Guide to Evidence Collection and Analysis.

Lincoln Rhyme’s textbook.

# # #

The perp was James Ferguson’s ex-wife.

In this case, Lincoln Rhyme allowed, this one case, motive was a pretty good clue and led them to the suspect: revenge.

Ferguson, along with Sachs, Sellitto and Marko, sat in Rhyme’s townhouse, filling in the details of what Rhyme had deduced an hour ago. He explained that he’d gotten divorced from his wife, Linda, about a year ago. She’d grown increasingly abusive and unstable, paranoid. She’d known his career was important to him before they got married but she’d still resented the long hours and his obsession with his TV production projects. She was also sure he was having affairs with his assistants.

He laughed bitterly. “Twelve-hour days don’t leave a lot of time or energy for that sort of thing.”

After the divorce her mental and emotional condition grew worse, he added, though it never occurred to him that she’d grow violent.

But she sure had. Coming up with a bizarre plan to get even with Ferguson by stalking and killing some of the women Ferguson dated or knew. She dressed like a homeless woman, so she wouldn’t be noticed, camping out near her intended victims’ apartments to get details about their lives. Then she’d murdered them using as a template Rhyme’s book, both to cover up any clues to her personally and also to shift the focus to Ferguson, since there was a record he’d bought a copy of the textbook.

The last step, tonight, would be to plant evidence implicating her ex-husband in Vicki Sellick’s apartment. A whole chapter in Rhyme’s book was about intentionally seeding evidence at a scene to establish guilt.

Rhyme glanced at his textbook, sitting in an evidence collection bag. “Why did you happen to buy it?”

Ferguson explained that as a documentary TV producer he watched as many competitors’ programs as he could. “I saw the episode on A&E about that murder in Florida, where you were talking about evidence. I thought it was brilliant. I thought maybe my company could do something along those lines. So I ordered your book. But I never got around to doing the show. I went on to other things.”

“And your wife knew about the book?” Sellitto asked.

“I guess I mentioned the project to her and that I was reading it. She’s been in my apartment off and on over the past year. She must’ve stolen it sometime when she was over.” He regarded Rhyme. “But why didn’t you think I was the one, like she planned?”

Rhyme said, “I did at first. But then I decided it wouldn’t’ve been smart for somebody to use a book that could be traced to them as a template for murder. But it’d be very smart for someone else to use that book. And whoever put this together was brilliant.”

“He profiled you,” Sachs said with a smile.