Point Of Origin by Patricia Cornwell was published in 1998.
Patricia Cornwell - Point Of Origin book description:
Carrie Grethen, partner in crime to William Temple Gault, has escaped from prison. Before she does so, she sends Kay Scarpetta a message that makes it all too clear she blames her for Gault's death, and has specific, if cryptic, plans for revenge.
Wary and quite shaken, Scarpetta still has to get on with an investigation into the death of an unknown female in a fire that has destroyed the isolated farmhouse home of her erstwhile political boss.
The post mortem reveals that the woman was stabbed before the fire was started, but while Scarpetta and her colleagues are puzzling over means and motive, they are called out to the scene of another fire and another murder. The pattern is the same, the answers as elusive, and then Benton disappears while following up a tip-off.
With appalling clarity, Scarpetta sees that Carrie has set up a scenario in which she can manipulate them all - and in which she appears to have the lethal upper hand.