“Kamal Gamal is known to Boston PD,” Baker said. “Picked up on rape charges in 1998. The complainant was a woman he met in a nightclub. She skipped and the case was dropped. Then in 1999, another rape case, this time involving a girlfriend. She was the Brazilian individual from whom Kamal Gamal stole the social and green card numbers for the card fraud that attracted Treasury’s interest. She was all set to testify but left for Brazil two days before trial. Ugly cases, both of them. Mutilation, pretty unusual stuff. The officer who worked the first case told me naturally he had suspicions that foul play was involved with the disappearance of the victim, but with no body and no relatives to speak of, it didn’t go anywhere. He did, however, get a warrant to search Gamal’s apartment.

“Forensics for a homicide, looking for typical biological evidence. Instead of finding blood or tissue residue in the drains of the sinks and the shower, lab finds trace amounts of powdered aluminum, carbon tetrachloride, and tetrachloroethylene.”

“Tetra-what?” someone asked.

“Hold on,” Baker said. “This is a homicide. Everyone’s looking for biological, so these items never got mentioned in the final lab report. I found out about them by talking to the original lab technician, who still had her notes. She indicated to me that carbon tetrachloride is basically fire extinguisher fluid, and tetrachloroethylene is dry-cleaning fluid. Powdered aluminum, it turns out, you can get in artists’ supply stores—they sell it as bronzing powder paint—”

“So let me get this straight,” April interrupted. “Kamal Gamal, cabdriver rapist, dry-cleans his shorts in his shower, refills his own fire extinguishers, and is looking to be Picasso.”

Laughter all around. “That’s one way of looking at it,” Baker said. “I was thinking the FBI lab might be able to come up with another interpretation. The original samples are gone, but we’ve still got the technician’s notes and report.”

“That’s enough for us to work with,” said an FBI agent across the table.

“I apologize for speaking out of turn,” said another agent, “but those are the ingredients for carbon-tet explosive.”

Two other FBI agents nodded.

“It’s a solvent,” one of them said. “Kind of like paint stripper. And it will blow up, just like paint stripper. But there is the question of why not just buy a solvent that’s out there on a hardware store shelf.”

“Isn’t there supposed to be an ATF person on this task force?” Baker asked.

“Part-time, not full-time,” someone said. “Plus, our esteemed colleagues at the Bureau of Alcohol, Tobacco and Firearms can be proprietary. Stretch a simple question into a deposition with a hundred objections.”