"Can you ascertain that this hasn't been changed since the last scheduled maintenance at Midsummer?" Miles asked the colonel.

The colonel shrugged. "The filters are not individually numbered, my lord. They're interchangeable, of course." He checked the report panel he carried. "No one in my department has done so, anyway. It's not due to be changed again till next month at Winterfair. It looks to have about the normal amount of accumulation for this point in its cycle."

"Thank you, Colonel. I appreciate your precision." He rose, and glanced at Illyan, who was watching stony-faced. "Your old office is next, Simon. Would you care to lead the way?"

Illyan shook his head, politely declining. "There isn't much joy for me in this, Miles. Either way your results come out, I lose a trusted subordinate."

"But wouldn't you rather lose the one who's actually guilty?"

"Yes." Illyan's snort was not wholly ironic. "Carry on, my Lord Auditor."

They trooped up three floors and down one to the level of Illyan's old office. If Miles had managed to surprise Haroche with his arrival in force, the general showed no sign of it. But was there maybe just a little discomfort in his eyes, as Haroche greeted his old boss and offered Illyan a chair?

"No, thanks, Lucas," said Illyan coolly. "I don't think we'll be here very long."

"What are you doing?" Haroche asked, as the colonel, practiced, went straight for the grille low on the wall to the right of his comconsole desk. The increasingly burdened forensics tech followed him.

"Air filters," said Miles. "You didn't think of the air filters. You've never been on space duty, have you, Lucas?"

"No, unfortunately."

"Believe me, it makes you very conscious of things like air circulation systems."

Haroche's brows rose as Weddell began vigorously spraying around the vent. He rocked back in his station chair, as-if-casually. He sucked thoughtfully on his lower lip, and did not ask, Have you considered my offer, Miles? He was a cool hand, and patient, and perfectly capable of waiting for the answer to emerge. No reason for him to flinch yet; whether the filters here were jammed full of vector encapsulations or not, it would prove nothing. Lots of people went in and out of Illyan's office.

"No," said Weddell after a moment. "Take a look for yourselves, gentlemen." He passed the black light along to Ivan and General Allegre.

"You'd think it would be here," commented Allegre, peering over Ivan's shoulder.

Miles had given it about a twenty-five-percent chance, personally, though he'd upped the odds after finding Galeni's vent clear. That left one of the conference chambers, or . . .

"Find anything?" asked Haroche.

Miles made a small show of going over and borrowing the hand-light from Ivan. "Not in here, dammit. I was hoping it would be simple. If the prokaryote vectors are caught in the filters, they show up bright red, y'see. We tested one, downstairs."

"What are you going to do next?"