Dr. Sophie Knowles teaches math at Henley College in Massachusetts, but when a colleague turns up dead, it's up to her to find the killer before someone else gets subtracted.

Math Professor Sophie Knowles shares her teaching venue with many other math and science faculty, most of whom she gets along with. But one in particular gives Sophie and her teaching assistant, Rachel, a hard time, thus annoying both women. When this colleague, a professor of chemistry, is found dead, poisoned in his office, Rachel is the prime suspect. It’s up to Sophie to put her talent for designing and solving puzzles to use to find his killer.

The Square Root of Murder

Dr. Sophie Knowles loves using puzzles to make math fun for students. But when winter seizes Henley College, she must thaw out a cold case to track down a killer--her most difficult puzzle yet . . . Winter Intersession is in full swing, and campus is buzzing over the concert celebrating the bell tower's reopening. The building has been shuttered for twenty-five years, and Sophie's shocked to learn why--a student leapt from it to her death. But she's even more troubled by the secrecy surrounding the case. After Sophie performs some quick calculations, she's left with a nagging question: Was it really suicide? When one of Sophie's favorite students, a performer in the concert, is brutally beaten and left in a coma, Sophie's mind kicks into overdrive. The horrific incidents seem too coincidental to be unrelated, but can Sophie put together the pieces from a twenty-five-year-old murder before any other students get hurt?

The Doctor and the Diva

When the Grim Reaper strikes the math department at a nearby university, P.C. and Mackenzie do some homework of their own and discover that almost everyone--parents, teachers, and students alike--had a motive to get this nutty professor out of the way.