A serial bomber appears to be targeting Miami's Colombian community. A wealthy importer of Colombian goods is discovered wearing an explosive collar; both he and Caine's mentor, a bomb technician, are killed in the attempt to disarm it.
The explosive device tests positive for TATP, which means that it was home-made and highly sensitive. The device is technically complex, with dummy switches, alternate power source, and collapsing circuits, indicating that it was constructed by a professional. The fact that the bomber used a photocell to defeat defusing confirms this theory.
An upscale Colombian antiques dealer becomes the second necklace-bomb victim. But this device is found to be a hoax designed only to lure the Bomb Squad into the proximity of a real bomb, found in the basket of a child's bicycle. On the child is found a strand of hair that comes from a toupee or wig; the boy confirms that a man with wavy black hair asked him to deliver the package in exchange for the bike.
The CSIs confirm the following things about the bomber: he is an expert in bomb making, he wears a toupee, and he constructs explosives out of counterfeit parts in proximity to insecticide. This leads them to the Miami Customs Impound Warehouse where counterfeit items and banned substances are confiscated, and where antiques and imports from Colombia must pass inspection. From a roster of people with access to the warehouse, Caine recognizes the name of Charles Berenger, a former bomb technician for the Miami Police Department, who was fired under strained circumstances. Berenger created the Colombian connection as a diversion-his real objective was revenge upon his former co-workers.