A picture was spreading outwards, so quickly that it seemed to expand like the advance of spilled water across the low, flat bench. Pieces of a jigsaw were connected with a steady, fluent rhythm, set in place by a childish hand, while Doctor Larkin watched and nodded quietly to herself. The first hint of a satisfied smile had already touched the corners of her mouth.

Julian was mumbling to himself in a subdued and childish voice, words obscure, but with the steady tempo of a memorised chant. He barely heeded the woman's presence at his side, content instead to discover the patterns that were taking shape on the polished tabletop - just as they had been inside his head.

This was unusual, his father recalled. In success and in failure, Julian rarely allowed himself to risk taking on a new endeavour without first glancing up at the nearest adult, to confirm that he would find approval in their eyes. The perspective of the remotely accessed image was mildly awkward, viewed from a downward angle on a standing screen that covered over half of the nearest wall. Its scope was broad, but only partially revealed the downcast faces of doctor and child in the neighbouring room.

Extraneous observers were a distraction, particularly if their presence served to make a six year old subject nervous. Quietly patient, the round-faced doctor had clearly outlined the reason why such measures were necessary - but offered this compromise when she saw him regarding her closely, with open doubt in his wide, dark eyes.

"What were you reciting, Jules?" asked Larkin, direct and probing.

The boy looked up. "Nothing."

Nobody else could be present for this mid-morning session, Hilary Larkin had explained to Richard in a calm but persistent voice. Not the nurses, technicians, consultants, or any of the hospital's other staff. And most particularly, not Julian's father. These tests were as important as their daily follow-up scans. "No more scanning for a short while yet. But this is easily as necessary as any medical test, especially to determine if we have successfully improved his cognitive abilities…"

"I have something here for you." Larkin held up a bulky padd with saturated tones of black and orange alternating around its border, like the stripes of a storybook tiger. Richard could not see what image it revealed, but he found that Julian had stopped, looking back with a touch of trepidation coming quickly to his eyes.

Hilary Larkin noticed it too. "It won't take long," she promised. "We can return to your puzzle as soon as we're done."

Sighing resignedly, Julian padded over to a smaller table in the corner. Larkin folded her legs into a crouch as she sat in the other of two child-sized chairs. "All right then." She showed the screen to the young boy sitting opposite. "Have a look at these shapes here. Which do you think would go best together?"

"That one." Julian poked the screen, twice. "And there. They started with the same shape - just folded in a different way."

"Very good," said Larkin, as the padd emitted a distinctive, bitonal chime.

Looking pleased, she tapped another command and turned the padd around to reveal a second set of images. Julian's response to every challenge was lightening quick, although with scant indication of any real interest. "Twelve out of twelve." Larkin sounded impressed, and Richard permitted his back to straighten, adopting a quietly satisfied smile. "Perhaps we ought to take it up another level."

Julian stared pensively downward and chewed his lower lip, focusing his attention on the activity of his own small hands as Larkin endeavoured to programme new instructions into her padd. The surge of pride that had fuelled his father's smile was just as immediately tempered by a rush of quiet concern.

Something's not right.

He noted that his son's right index finger had begun to trace a path over a jagged crack on the table in front of him. "Father said…" he began.

"Said what?" Even Doctor Larkin's efforts had gradually slowed, and halted. She set the padd face down across her knees. "You can tell me, Jules. What did he say?"

Julian's reply was soft and faltering. "He said that you would tell us when it's time to leave," he ventured, hopefully. "Is… Is that soon?"

"It depends on how your tests go." At least the woman was honest. "I wouldn't want to make any promises."

Nodding quietly, Julian wiped a sleeve across his eyes.

"When you're older-" Larkin continued. "You'll probably be glad that we saw your treatments through to the end. And you managed to do that puzzle just fine, and all of these other tests. Isn't everything so much easier now?"

"I guess…" But to Richard's ears, the answer sounded a little too forced - a little too brave.

"Well, if not, then why do you think we're doing all of this?"

"Father told you to," Julian began in a small, trembling voice. He bowed his head and continued to pluck fragments of lint from his loose white gown. But his face was clear on the surveillance screen, separated from Richard as if by no more than the pane of a clear aluminium window.

"He brought me here because he didn't like me any more."

"That's not it!" Patrick's voice was rising to a whine as Naron led Bashir on their return to his principle office. "No, Jack - you're doing it wrong."

Entirely unfazed by their reappearance in the doorway, three of Julian's party had clustered at one of the terminal screens, where Jack was jabbing with increasing frustration at the unresponsive interface. Sarina stood apart and trailed a hand along the raised edge of the same curving desk. She kept her eyes averted, revealing little of the thoughts behind them. But she had stopped as the door opened to allow the pair to enter.

"He's right, you know," confirmed Lauren. "You have to set up an adaptive algorithm before you can decipher that…"

"Will you get off?"

The memory of Jack's impulsive demand echoed and faded in the now-silent room.

"You may still ask how to access our security protocols." Could there have even been a touch of amusement in Naron's response? Bashir fancied so, even as he hesitated less than a metre from the entrance. Was he finally accustoming himself to the nuances of Adigeon expressions? Or was that, like many things, no more than the vagrancies of his own imagination, attempting to make connections where none existed?

"I can give you the means to get inside, once you reach your destination." Naron spoke directly to him, although he had adopted a sidelong stance to keep the other off-worlders within his sight. "But that is as far as my authority extends. I still have duties to perform, commitments which I cannot fail to meet. To do so would doubtless attract the attention of my superiors. I will not be able to accompany you to journey's end."

"I say we make him come with us," insisted Jack. "Unless we want the whole planet to know that we were here."

Naron turned calmly to face him. "I gave my word."

"Whatever that's worth."

Bashir reached up with a shaking hand, to clutch his stomach where it had long since started to ache. The pain was making him dizzy. Tentatively, he extended his other arm until his fingertips brushed against the wall behind him. He knew - he knew - what promises meant on this world. His voice was soft, with little support, but it did not fail him. "Then, there is something you can…?"

"Move aside," Naron told Jack as he moved to displace the three at his main office console. Lauren smiled to see him so close, briefly passing her own gaze up and down the pale Adigeon. But Jack's scowl of irritation was as dark as his eyes. For a moment, though, he gave no further challenges.

"I trust that every one of you is already committing this pass-key to memory," said the pale Security man as he tapped a sequence of controls - each with a distinctly different tone in the otherwise silent air. A weak yellow beam issued forth from the computer panel to sweep over his semi-translucent, off-white skin. And as this faded, more lights began to swirl in a complex, mathematically meticulous pattern within a shallow compartment at his side.

They were coalescing, Bashir realised. Transforming themselves to a solid mass which the angle of the desk was not permitting him to see.

"This holds the code."

Patrick leaned forward, eager curiosity in his eyes, as the Adigeon reached inside. But Bashir frowned dubiously at the object in Naron's slender, knobbled hand. "A hypospray?"

"The process is quite simple," the other man explained, ignoring the frown upon the oldest Human's brow. "It introduces a precise sequence of amino acids into your blood, encoded to interact with our scanners in a very specific manner. These are the codes that our security systems detect, once the data is gathered, of course. I promise, there is very little risk of harm."

Bashir raised his eyebrows, oddly intrigued. His mind had been slow to register the implications of Naron's words. Slower than he thought it should have been. But he was sure he'd read something about… Spies used similar devices on occasion, didn't they? As a means to encode the secrets they had stolen. When would such specialised technology have been introduced to this hot, cloud-smothered world?

"…And use it to track our movements, I suppose," Jack demanded loudly. "Hm? That's exactly what they'll do."

When he finally responded, Naron's naturally low, husky voice had dropped to a hiss - barely reaching even the artificially enhanced perception of his visitors. "If it would lessen your anxiety-" His speech had accelerated noticeably, losing its level, regular cadence for the first time since the Humans' arrival. "Place the contents through a chemical analysis. Otherwise, trust me. Or turn back. There are no other options open to you."