Napier's Bones (Bonnie Pinkwater Mysteries)

When a skeleton is unearthed in a field next to East Plains High School, math teacher Bonnie Pinkwater is thrust into a three-decade-old murder. What she uncovers are Satanists, ruthless mercenaries, murderous homecoming queens, a crazed mother, a fateful blizzard, and the death of someone near and dear to her. As her once considerable gifts of memory and deduction are eroded by the trauma of loss, Bonnie must solve a thirty-year-old cold case before the killer decides the best way to remain free is to add one female mathematician to his list of victims.
Book 5 in the Bonnie Pinkwater series.