The FBI profiling team is called to Florida where a seres of efficient bombs killed every single target; this rules out a terrorist or politically motivated bomber.
The bombs themselves carry the signature of Adrian Bale, a master-bomber who was jailed after taking out six FBI agents in Boston, who even pushed the next button when he knew it would only worsen his sentence.
Then there's a lead to an alternative scenario: master forger David Walker, who had to commit a single murder to keep out of jail but covers it up by playing the Bale copycat.
Or is there a link between these two suspects, perhaps via a Internet forum which contains suspicious messages?