anual abort?" Susan stared at her screen,mystified.

She knew she hadn't typed any manual abort command—atleast not intentionally. She wondered if maybe she'd hit thewrong sequence of keys by mistake.

"Impossible," she muttered. According to the headers,the abort command had been sent less than twenty minutes ago. Susanknew the only thing she'd typed in the last twenty minutes washer privacy code when she'd stepped out to talk to thecommander. It was absurd to think the privacy code could have beenmisinterpreted as an abort command.

Knowing it was a waste of time, Susan pulled up her ScreenLocklog and double-checked that her privacy code had been enteredproperly. Sure enough, it had.

"Then where," she demanded angrily, "wheredid it get a manual abort?"

Susan scowled and closed the ScreenLock window. Unexpectedly,however, in the split second as the window blipped away, somethingcaught her eye. She reopened the window and studied the data. Itmade no sense. There was a proper "locking" entry whenshe'd left Node 3, but the timing of the subsequent"unlock" entry seemed strange. The two entries were lessthan one minute apart. Susan was certain she'd been outsidewith the commander for more than one minute.

Susan scrolled down the page. What she saw left her aghast.Registering three minutes later, a second set of lock-unlockentries appeared. According to the log, someone had unlocked herterminal while she was gone.

"Not possible!" she choked. The only candidate wasGreg Hale, and Susan was quite certain she'd never given Haleher privacy code. Following good cryptographic procedure, Susan hadchosen her code at random and never written it down; Hale'sguessing the correct five-character alphanumeric was out of thequestion—it was thirty-six to the fifth power, over sixtymillion possibilities.

But the ScreenLock entries were as clear as day. Susan stared atthem in wonder. Hale had somehow been on her terminal while she wasgone. He had sent her tracer a manual abort command.

The questions of how quickly gave way to questions of why? Hale had no motive to break into her terminal. Hedidn't even know Susan was running a tracer. Even if he didknow, Susan thought, why would he object to her tracking some guynamed North Dakota?

The unanswered questions seemed to be multiplying in her head."First things first," she said aloud. She would deal withHale in a moment. Focusing on the matter at hand, Susan reloadedher tracer and hit the enter key. Her terminal beeped once.

TRACER SENT

Susan knew the tracer would take hours to return. She cursedHale, wondering how in the world he'd gotten her privacy code,wondering what interest he had in her tracer.

Susan stood up and strode immediately for Hale's terminal.The screen was black, but she could tell it was not locked—themonitor was glowing faintly around the edges. Cryptographers seldomlocked their terminals except when they left Node 3 for the night.Instead, they simply dimmed the brightness on their monitors—auniversal, honor-code indication that no one should disturb theterminal.

Susan reached for Hale's terminal. "Screw the honorcode," she said. "What the hell are you up to?"

Throwing a quick glance out at the deserted Crypto floor, Susanturned up Hale's brightness controls. The monitor came intofocus, but the screen was entirely empty. Susan frowned at theblank screen. Uncertain how to proceed, she called up a searchengine and typed:

SEARCH FOR: "TRACER"

It was a long shot, but if there were any references toSusan's tracer in Hale's computer, this search would findthem. It might shed some light on why Hale had manually aborted herprogram. Seconds later the screen refreshed.

NO MATCHES FOUND

Susan sat a moment, unsure what she was even looking for. Shetried again.

SEARCH FOR: "SCREENLOCK"

The monitor refreshed and provided a handful of innocuousreferences—no hint that Hale had any copies of Susan'sprivacy code on his computer.

Susan sighed loudly. So what programs has he been usingtoday? She went to Hale's "recent applications"menu to find the last program he had used. It was his E-mailserver. Susan searched his hard drive and eventually found hisE-mail folder hidden discreetly inside some other directories. Sheopened the folder, and additional folders appeared; it seemed Halehad numerous E-mail identities and accounts. One of them, Susannoticed with little surprise, was an anonymous account. She openedthe folder, clicked one of the old, inbound messages, and readit.

She instantly stopped breathing. The message read:

TO: NDAKOTA@ARA.ANON.ORG

FROM: ET@DOSHISHA.EDU

GREAT PROGRESS! DIGITAL FORTRESS IS ALMOST DONE.

THIS THING WILL SET THE NSA BACK DECADES!

As if in a dream, Susan read the message over and over. Then,trembling, she opened another.

TO: NDAKOTA@ARA.ANON.ORG

FROM: ET@DOSHISHA.EDU

ROTATING CLEARTEXT WORKS! MUTATION STRINGS ARE THE TRICK!

It was unthinkable, and yet there it was. E-mail from EnseiTankado. He had been writing to Greg Hale. They were workingtogether. Susan went numb as the impossible truth stared up at herfrom the terminal.

Greg Hale is NDAKOTA?

Susan's eyes locked on the screen. Her mind searcheddesperately for some other explanation, but there was none. It wasproof—sudden and inescapable: Tankado had used mutationstrings to create a rotating cleartext function, and Hale hadconspired with him to bring down the NSA.

"It's…" Susan stammered. "It's… not possible."

As if to disagree, Hale's voice echoed from the past: Tankado wrote me a few times… Strathmore took a gamble hiringme… I'm getting out of here someday.

Still, Susan could not accept what she was seeing. True, GregHale was obnoxious and arrogant—but he wasn't a traitor.He knew what Digital Fortress would do to the NSA; there was no wayhe was involved in a plot to release it!

And yet, Susan realized, there was nothing to stophim—nothing except honor and decency. She thought of theSkipjack algorithm. Greg Hale had ruined the NSA's plans oncebefore. What would prevent him from trying again?

"But Tankado…" Susan puzzled. Why wouldsomeone as paranoid as Tankado trust someone as unreliable asHale?

She knew that none of it mattered now. All that mattered wasgetting to Strathmore. By some ironic stroke of fate,Tankado's partner was right there under their noses. Shewondered if Hale knew yet that Ensei Tankado was dead.

She quickly began closing Hale's E-mail files in order toleave the terminal exactly as she had found it. Hale could suspectnothing—not yet. The Digital Fortress pass-key, she realizedin amazement, was probably hidden somewhere inside that verycomputer.

But as Susan closed the last of the files, a shadow passedoutside the Node 3 window. Her gaze shot up, and she saw Greg Haleapproaching. Her adrenaline surged. He was almost to the doors.

"Damn!" she cursed, eyeing the distance back to herseat. She knew she'd never make it. Hale was almost there.

She wheeled desperately, searching Node 3 for options. The doorsbehind her clicked. Then they engaged. Susan felt instinct takeover. Digging her shoes into the carpet, she accelerated in long,reaching strides toward the pantry. As the doors hissed open, Susanslid to a stop in front of the refrigerator and yanked open thedoor. A glass pitcher on top tipped precariously and then rocked toa stop.

"Hungry?" Hale asked, entering Node 3 and walkingtoward her. His voice was calm and flirtatious. "Want to sharesome tofu?"

Susan exhaled and turned to face him. "No thanks," sheoffered. "I think I'll just—" But the words gotcaught in her throat. She went white.

Hale eyed her oddly. "What's wrong?"

Susan bit her lip and locked eyes with him. "Nothing,"she managed. But it was a lie. Across the room, Hale'sterminal glowed brightly. She'd forgotten to dim it.