MONNIE HAD AN ADDRESS for the hacker in Dale City, Virginia, only about twelve miles from Quantico. The agent who’d fielded the original call hadn’t followed up very well, which bothered us, so we figured the agent wouldn’t mind if we did his job for him.

I wasn’t actually planning on taking Monnie along, but she wouldn’t have it any other way. So we dropped her SUV off at her house and she rode with me to Dale City. I’d already called ahead and spoken to the girl’s mother. She sounded nervous, but she said she was glad the FBI was finally coming to talk to Lili. She added that “nobody can ignore Lili for long. You’ll see what I mean.”

A young girl in black coveralls answered the front door. I assumed she was Lili, but that turned out to be wrong. Annie was the twelve-year-old sister. She certainly looked fourteen. She beckoned, and we stepped into the house.

“Lili is in her laboratory,” said Annie. “Where else?”

Then Mrs. Olsen appeared from the kitchen and we introduced ourselves. She had on a plain white blouse and a green corduroy jumper. She was holding a greasy spatula, and I couldn’t help thinking how casual the domestic scene was. Especially if what Lili thought she had come upon was real. Had a fourteen-year-old found a possible trail that would lead us to the kidnappers? I’d heard of cases solved in stranger ways. But still . . .

“We call her Dr. Hawking. Like Stephen Hawking? Her IQ is up there,” said her mom, poking the cooking utensil upward for emphasis. “Smart as she is, Lili lives on Sprite and Pixie Stix. There’s nothing I can do to influence her dietary habits.”

“Is it all right if we talk to Lili now?” I asked.

Mrs. Olsen nodded. “So I guess you’re taking this seriously. That’s so wise with Lili. She’s not making any of this up, believe me.”

“Well, we just want to talk to her. To be on the safe side. We’re not sure that this is anything, really.” Which was true enough.

“Oh, it’s something,” said Mrs. Olsen. “Lili never makes a mistake. She hasn’t so far, anyway.”

She pointed the spatula up the stairs. “Second door on the right. She left it unlocked for a change, because she’s expecting you. She instructed us to stay out of it.”

Monnie and I headed upstairs. “They have no idea what this could be, do they?” she whispered. “I almost hope it’s nothing. A false lead.”

I knocked once on a wooden door that sounded hollow.

“It’s open,” came a high-pitched female voice. “Come.”

I opened the door and looked in on a pine bedroom suite. Single bed, rumpled cow-pattern sheets, posters from MIT, Yale, and Stanford on the walls.