“Doesn’t seem it will,” the young man said. “There could be a way to fix it, but nobody seems to have the technology to do that at this point. In any case, there’s no heavy-water generator at the dam . . . Connie, this whole thing doesn’t smell right.”

“You think the files are some kind of trap, like the one set in the office?”

“I think this disk is more than it seems.”

“What do you mean?”

“The picture files, take a look at them.” Chang flashed a series of images on the laptop screen.

Carson would have shrugged if her arm and shoulder had functioned. “It looks like an office, the office at Sindhu.” The image of the place was seared on her retinas, along with a picture of Jean-Marc, lying there, eyes staring blankly into space.

Chang said, “Do they look like anything you’d want to encrypt? A picture of a desk, a chair, a table?”

“Maybe they were just keeping them on the same disk.”

“Maybe. Or they might be something else. I mean, why put these innocent-looking photos in with a file that’s so complex? I decided there must be another layer, beneath the images.”

“But how would you find out if—”

“Steganography,” Chang said. “It can embed information into a file, but getting it back isn’t just a matter of running a simple cracking program—you have to figure out how it was done, because there are so many different ways. I tried a couple of approaches while you were out of it, and I finally got a handle on it with the Digital Invisible Ink Toolkit, and there’s definitely embedded information in this picture. So I’ve got it, but it’s encrypted, too.”

“And you don’t have the encryption key.” Wheels within wheels, Carson thought. How many layers would they have to penetrate?

“Not yet,” Chang said. “This is an old-style pencil-and-paper cipher—you can tell because it’s just letters—but, wait a minute, look at the letter frequencies! I haven’t seen one of these in years, but I think this might be a Playfair cipher.”

“Playfair?” Carson said. “Spies used it, a long time ago—in World War II, right? How do you find the encryption key?”

“If it’s Playfair, it’ll be a group of 10 to 15 unique letters. It could be a single word, but sometimes it’s, say, a long phrase in a book, a song lyric—”

“A phrase all the members of the group would have to know.”

Chang nodded. “Anyone who needs to decode messages.”

“Wiki, you called the technology, for the heavy-water reactor, the ‘copper bracelet.’ Right?”

“Yeah.”

“When we were in France, the ‘copper bracelet’ was an actual physical copper bracelet. Jewelry.” As she spoke, Carson tried to circle her left wrist with her right hand. The effort made her gasp. “There were words engraved on it, in Hindi, or—”