Vicki had thought the same thing, when she and Reheema were following the dealers the past two days. It was almost primitive.

"HIDTA starts with a normal cell phone, one that's seized, let's say, during a search. They call that the ‘known phone.' They analyze the data in it, like the directory, and figure out the phone numbers associated with each person called. You follow?"

"Yes."

"Then they subpoena the records for the known phone, over a long period of time, and they load all the information about the calls into the computer. The program they wrote generates a Call Frequency Chart. That is, it makes a record of how often the owner of the known phone calls certain numbers." Dan ran a fingernail across the first line of the list. "This first page is a sample, and you can see the first name on this list is Lik, which they tell me is the nickname for Malik."

"Okay."

"Lik's number is this one, and the chart shows that the owner of this phone called Lik's number the most frequently of all other calls, in a month's time. The column on the far right is the number of times the owner of the phone called Lik in a month, which is 354. You can look down the chart at the first three people the owner called the most. Lik, Tay, and Two. See? He called them 354, 322, and 310 times, respectively."

Vicki did.

"Now, they tell me that drug dealers change cell phones all the time. They use ‘burnout phones' or ‘drop phones,' they call them. Let's say the owner of the phone, the bad guy, drops this phone. He throws it away to avoid the cops."

"Okay."

"The problem used to be that when the bad guy discarded a phone, all the investigation of his activity and calls were gone, and HIDTA would have to start over again. No more." Dan went to the next sheet of numbers. "Now they can figure out which cell phone he picks up next, using this software."

"How?"

"Because, as a logical matter, he tends to call the same set of people he called before, at the same frequency. See this second chart? This new caller called Lik's number ten times that day. HIDTA does the same thing for the other people called, Tay and Two, and they do it over a long period of time, to enhance the reliability of their conclusion. The odds are that it's the same person making those calls, regardless of which phone he uses. Correct?"

"Correct."

"So then we can reason backward, and say that therefore, the bad guy is now using this cell phone. We can figure out that that's his new cell number and pick up activity on the new phone, losing no time on the investigation. In other words, the fact that they change phones doesn't defeat us."

"Great."

"Now this software has other applications for investigations. For example, what they told us at the meeting is that your cell phone, with the blue daisies"-Dan smiled-"is currently being used by a known mid-level drug dealer. His name is Ray James."

"What?" Vicki was astonished. "How do they know that?"

"Here's his chart, but it's only for a few days, so it's not rock-solid by any means." Dan set two charts side by side. "But see? They had Ray James's known phone from a previous arrest, and they did a Call Frequency Chart for him on the known phone. Then, because they knew your cell number, they began a Call Frequency Chart for your phone after it was stolen."

"So they tapped my cell phone?"

"No, they don't have to tap the phone to get this. They just can get a pen register, a record of calls made by the phone, as opposed to actually listening in to the call."

"Okay."

"So now they load your Call Frequency Report into the computer and ask it for a match, and it comes up with Ray James. In other words, Mr. James, who used to use this known phone"-Dan pointed to the chart on the left-"is now using your phone, because his old Call Frequency Chart matches the one for your phone, on the right."

"My God." Vicki's eyes widened. "So they know Ray James killed Reheema's mother!"

"Not yet."

"But they go and pick him up and question him about the murder, don't they?" Vicki was so tempted to call Reheema, but she couldn't. "Either he killed her or he knows who did!"

"Slow down. They don't do that yet. Why are you getting so excited?"

"But it was only days ago! It's most likely him! Ray James could be the guy with the gravelly voice, that we both talked to!"

"Vick." Dan smiled and held up a warning hand. "Settle down. You know better than that."

"I do?"

"Yes, you do. Think about it, calmly. All it means is that Ray James has the phone from somebody who might know that. Or that Ray James found the phone in a Dumpster or on the street. Or that he bought it from somebody who bought it from somebody else who found it on the street after the killer threw it there." Dan cocked his head, his blue eyes tired. "All we really know for sure is that Ray James has your cell phone."

"We can still ask the man, can't we?"

"Not consistent with that pesky Constitution, we can't. ATF can't, and they won't." Dan laughed. "This is way too soon to be sure, and they don't show their hand until they have the goods. You should know that they would need to show a judge at least a few months of calls to establish probable cause." Dan smiled. "So your phone is hard at work for the common good."

"So what will they do about Ray James?"

"Try to learn more about him, build their case, record his calls. Do it right."

"He has a record?"

"Ag assault, firearms, possession and distribution, the works. His record's in my briefcase; they gave us all copies. They'll follow up, it's just a question of time. You know how they investigate. Morty was the most methodical agent I knew."

Morty. Vicki tried to simmer down. "Ray James doesn't bring us any closer to Morty's killer."

"Not really, no."

"And he's on the back burner."

"For the time being. Then the heat will die down, but they won't forget about him. I won't let them." Dan began to gather his charts. "But we have been told to deal with Toys ‘R' Us, top priority. I put a press release together for Strauss. There's a conference at eleven tomorrow. Everybody's gonna be there, from the mayor on down." Dan put the charts into his briefcase. "Plus, I forgot, they do have the one other guy, a loose end. This guy who was with Browning. They said they'll track him down when they get the chance."

"What guy? The guy who got shot, that one? I thought he was killed."

"No, not that one, another one. Tall guy, walked out of the store with Browning. The FBI thinks he mighta helped set him up for the kill. They're lookin' for him everywhere."

Huh? "I didn't see him on TV."

"He's there, walking with Browning. They picked him up on the surveillance cameras at Toys ‘R' Us. He had some kinda cap on and they only got his back."

Oh no.

"Tall guy, black, that's it. He ran when the shooting started."

Reheema.

"And they're looking for a car that was waiting for him. They got a shot of it on the surveillance camera. He was working with another guy and he ran to him and the car when the shooting started."

That would be me. "Could they ID the other guy?"

"No. Short white guy. The FBI thinks this new gang is multiracial. Gives you hope, doesn't it?"

Eeek. "Did they get the make of car?"

"I think so, but no plate either." Dan slipped the charts into his briefcase, then straightened up with a smile. "No more work for today."

The FBI was looking for Reheema and her, cross-dressing.

"Do you know how nice it is to come home to you?" Dan reached for Vicki and pulled her into his arms, kissing her softly. "You made me very happy today, on what could have been the worst day of my life."

Aw. "Really?"