Daddys Girl by Lisa Scottoline

Natalie Greco loves being a teacher, even though she can't keep her students from cruising sex.com during class. She loves her family, too, but her boyfriend fits in better with the football-crazy Grecos than she does. Then a colleague, handsome Angus Holt, talks Nat into teaching a class at a local prison, and her world turns upside down.

A violent prison riot breaks out, and Nat rushes to save the life of a mortally wounded guard whose last words are: "Tell my wife it's under the floor." Nat delivers the cryptic message, but before she knows it, she's suspected of murder and hiding from cops and killers alike. She is forced on the run to solve the riddle of the dead man's last words and to save her own life—and find real love.