Used book – The Eyes of Darkness, Dean R. (Ray) Koontz

Eleven-year-old Danny died in a horrific bus accident. At least, that's what the police tell his mother, Tina Evans, advising her not to identify the horribly mutilated little body. But a year later, Tina finds a message from her son written in chalk on his blackboard. A manifestation from beyond the grave? A macabre joke? Is she going mad? Or could it be... Tina wants to get to the bottom of it: she asks for the grave to be reopened. Within the hour, the secret service tries to assassinate her...