"When you're hungry," she said.

The talking to herself was intentional and something Katie used often. Everything about Katie's approach to this case had been thought through in advance, from the net curtains she'd recently put up to stop the man from losing himself in the Mediterranean beyond her window to the Sicilian sweets and the clothes she currently wore. A selection so neat and anonymous that even she had to look at them to remember exactly what she was wearing.

There'd been a suggestion, from her as it happened, that Prisoner Zero might respond better to a male psychiatrist. It had been made in the panic following her first meeting with the man and she'd had the sense not to push it when Petra Mayer disagreed. Having seen how Prisoner Zero shut down in the presence of Miles Alsdorf, she could only concede that the Professor had been right.

"We're going to do it differently today," said Katie. Actually they were going to be doing it differently every day until she finally hit on something that worked. Dr. Katie Petrov knew all the reasons why consistency was good. She'd done the lectures on building trust without establishing dependency. Hell, she'd written some of them, but he was running out of time and elective autism was a poor defence.

It was surprising the number of attorneys who assumed that a sudden descent into silence by their client would pass for evidence of mental trauma. Every half-bit stalker with a knife and a grudge, every thirty-something sleazebag who saw kindergarten gates as the entrance to heaven...

She was getting angry, mostly with herself, Katie realized. A sign of helplessness and very unlike her. Katie didn't get emotional at work. Not even when working with anorexic adolescents and statistically they were more likely to push industry professionals over the edge than anyone else.

"The thing is," Katie said, "you've only got ten days. I don't know if anyone's explained that?" She caught it then, a quick flicker behind his dark eyes. "Oh," said Katie, as she picked up what looked like the bag for a laptop, "I see. Everyone's told you that, have they?"

A cricket outside her window gave the only answer.

Opening the case, Katie pulled out a small silver box that trailed a mains lead. "I'd like to use this," she said. "It's not compulsory but it would help me help you." She held out the device. "Do you want to take a look?"

Sixty seconds later Katie let her hand drop.

"Electrodes," she explained, extracting a tangle of wires from the small case and putting them carefully on her desk. "This is a basic electroencephalograph. I use it mostly for kids with Ritalin dependency. It helps them learn to normalize certain brain patterns. Obviously that's not what I want to try with you..." There was a pause, the expectant kind. One Prisoner Zero was meant to fill.

"No problem," said Katie. "Would you like me to put them on for you?"

Outside her door waited two marines. Tall men with aubergine skin and cropped skulls, a rifle each and fat body armour. In their right ears they wore single black beads, button mikes were taped to their throats.

Either one would have held the captive down while the other helped Katie glue electrodes to his skull, and they'd have done it willingly and probably regarded Katie in a better light afterwards. Katie found the fact she wanted that approval unnerving. Almost as unnerving as realizing it was prompted by an unspoken fear that the marines regarded Katie as somehow against them.

"I'm here to help," Katie said. "I can do that better if you wear these." She nodded to the spider's web of wires. "All the box does is measure brain activity. It won't tell me your secrets or let me look inside your head." She spoke as she might to some drug-addled gang-banger in need of a quick and dirty court report. Casual did it, anything else and most of them retreated into a carapace harder than any which nature could produce.

Katie was still trying to work out exactly why she got this gig. At twenty-seven she was young to be doing this kind of analysis and her pro-bono work for Médecins Sans Frontières was well known. She'd been the only specialist prepared to go on CNN and say the outbreak of unquestioning patriotism which followed the attempt to shoot the President was bad for America's health.

It made her an obvious choice when Petra Mayer, President Newman's unofficial conscience, began looking for an independent expert to balance the expert already produced by the Pentagon. While at the same time rendering her opinion worthless to most of the Supreme Court, the majority of whom had been appointed by the previous incumbent.

So was her evidence meant to be taken seriously or had she been hired to jump through hoops? And, if so, was her old tutor part of that plot? There were levels to this Katie couldn't begin to imagine, she knew that. And rumours enough to keep conspiracy theorists busy for years.

That Prisoner Zero was the First Lady's bastard brother was one of the best. A slightly less fanciful one had the Pentagon knowing exactly who he was but refusing to tell the White House.

Whatever the truth, she'd been handed a poisoned chalice that might still turn into one of the decade's plum jobs. How many psychiatrists of her age could say they'd been retained to evaluate the mental state of a man on trial for trying to kill the President? Come to that, how many of any age...

Picking up the wires, Katie reached for a tube of surgical glue and smeared an electrode, sticking it to one side of the prisoner's skull. When Prisoner Zero didn't complain, Katie stuck another to the opposite side. His lack of complaint was a benchmark. The moment he shrugged her away was the point Katie would stop fixing the wires.

It helped that Prisoner Zero's head was recently shaved. Most of the kids she handled pro bono had hair twisted into topknots or cut to some gang pattern. For a few of the more vain, deciding whether or not to let Katie fix her wires took longer than they put into deciding their plea.

"Okay," Katie said, when the last wire was in place, "I'm going to say words and you're going to tell me the first thing that comes into your head. It can be a memory or reaction. Something from childhood or something from now."

So slow were the pupils which watched her that for a second Katie was worried the marines might be drugging him, but then the breeze lifted a corner of the net she'd pinned in place and, as Prisoner Zero's head flicked towards the movement, his pupils collapsed like stars swallowing themselves.

"Mother," Katie said. "What does that word suggest to you?"

A bottle empty on a table.

"It's all right," said Katie, "you can tell me."

Checking a readout on her EEG, Katie noted how high one of the columns had gone. Someday some genius would work out how to translate results into direct evidence and half her job would disappear overnight. "Okay," she said with a sigh, "let's try another... Cat."

His lover at a pavement café feeding scraps from her plate to a sack of bones then shooing away the ragged child who came trying to beg coins. Amber eyes hurt in the twilight.

"Sun."

Brightness lancing through cracks in a study door and burning a thousand planets of dust, spinning and chaotic, tied by laws he was only just beginning to understand.

"Water."

A skin of liquid on the underside of an Amsterdam fountain clinging to the marble's hard bone and curving away into its own event horizon.

"You."

"What?" demanded Katie, leaning forward. With an effort she made herself sit back and move on to the next word. There had been something there, something the man wanted to say, Katie was sure of it.

"Feathers."

A dream-catcher made from a boa found in a biscuit tin. Celia left it on the wall when she went.