When at last he found what he was looking for, the realization almost knocked him out of his chair.

“Why, you smarmy sonofabitch!” he muttered triumphantly, seeing the similarity between one of the mutations Crusher had isolated and an illustration from a paper presented at the Federation Medical Academy over a dozen years before. “I’ve got you now! I told them there’d be a signature!”

He pushed a button on the arm of his chair and it floated gently off the floor and hovered on a cushion of air. The chair had been a gift from Spock some years ago after McCoy had reached 125, an acknowledgment that the doctor’s human legs were not as strong as they once were. McCoy zoomed across the room to the comm unit and, not bothering to check what time it was in San Francisco, opened a frequency.

“Nyota, Beverly?” he shouted, his voice shaking with excitement. “Come on, ladies, get on the horn. I’ve got him! I know who created this goddamn bug. I’ve found the signature. Where’s Selar?”

“Nothing like what you’re describing,” Dr. Sekaran told Selar when the Listener had left them alone in the heart of the medical dome on Tenjin V. “The only unusual event we’ve had in the past year or more was a cluster of cases of a bizarre carcinoform that occurred simultaneously in several of the domes, then disappeared just as quickly.”

Sekaran was in essence the senior physician for all of Tenjin. His headquarters, at the heart of a dome in the central government complex, was as busy in its own way as the myriad mercantile domes it serviced. Here Sekaran and his multiplumaged staff monitored the health of every citizen on the planet, though visiting tourists, he admitted, were more difficult to track.

Selar studied the readouts scrolling down the clearsteel walls of the medical complex, her practiced eyes searching for something commensurate with the specimens she and Crusher had thus far identified.

“Probably not at all what you’re looking for, but you did say you wanted everything,” Sekaran went on. “It popped up unexpectedly two seasons ago—anything transmissible is unexpected here, because the atmosphere is filtered more carefully than even on a starship. We simply can’t let something contagious get loose inside even one of the domes, because they’re all interconnected by the travel tubes. As a result, we’ve become so accustomed to the filtration systems that we’ve been spoiled. Even a common cold could kill some of us.”

“Understood,” Selar said, studying the specific dataset Sekaran indicated. “You did say the entity was a carcinoform?”

“It was quite bizarre,” he said. “People turned up at clinics complaining of chills and fever but, on examination, were found to have a rapidly forming cancer that started in the lungs and metastasized to the rest of the major organs. Tests showed no evidence of unusual bacteria or viral infection. Yet people in close proximity—family, coworkers—would ‘catch’ this from each other as if it were a flu bug.”

“When you say rapidly forming…” Selar began.

“Days. Often in less than forty hours of onset of symptoms. I’ve never seen anything move so fast in my entire career. Germs are supposed to do that, but not cancers. And cancers are not supposed to be contagious.”

If Selar was shaken by this information, she gave no sign. “I believe, Dr. Sekaran, we can abandon our parameters of what is ‘supposed’ to happen where this entity is concerned.”

“So you think it’s related to the bug you’re trying to track?”

“Possibly. I will need access to this data in order to run more tests.”

“If your medscanner can interface with our system, you’ll have it,” Sekaran said.

Back on the ship, it was clear from the aromas that Sisko had found his eggplant. Albatross’s galley was barely big enough for him to turn around in, but, having gathered all the ingredients he needed on Tenjin, he was making magic there.

“Step right up, ladies and gentleman,” he announced, spooning something savory and steaming over plates of fluffy white rice. “No replicated rations tonight. This evening’s main entree is freshly prepared, completely vegetarian, and guaranteed to please the most demanding palate.”

“What is it?” Selar asked, inhaling appreciatively before taking her plate to a nearby console where she could work on Sekaran’s data while she ate.

“Eggplant ratatouille ,”Sisko explained, watching for the nods of approval as each one tasted his masterpiece. “Baby eggplant sauteed in virgin olive oil with finely chopped Vidalia onions and fresh garlic, then blended with carrots, plum tomatoes, three kinds of bell peppers, a few new potatoes, some zucchini, cilantro, cayenne, and, well, a few secret ingredients of my own, and simmered to perfection.”

“Excellent,” Selar remarked.

“Indeed,” Tuvok concurred. “All of this from ingredients gathered on Tenjin?”

“Not counting my own secret spice blends,” Sisko grinned. “I have my own herb garden on Okinawa.And I never go anywhere without some. I sure hope I haven’t violated the Prime Directive by comparing recipes with the Tenji,” he added with a wink, “although the restaurant did call itself the Interplanetary Café, and I could swear the sous-chef with the blue feathers had a distinctly Cajun accent…”

He stopped himself and blinked at Zetha, who had finished her portion in the time he’d been talking. “Did you even taste what you just ate?”

“It’s good,” Zetha said as if stating the obvious, wiping her plate inelegantly with her fingers to get the last of the tomato sauce. “Is there more?”

“Don’t know where she puts it!” Sisko marveled, doling out a second helping and watching her attack that with equal gusto. “If you’re going to eat with your fingers planetside, no one will ever mistake you for a Vulcan.”

“I’ll remember that,” Zetha said with her mouth full. “But where I come from, when there’s food, you eat it.”

Sisko still wasn’t sure he believed she had simply been plucked off the streets of the Romulan capital and sent to them on a mission of mercy. He intended to have a little chat with Tuvok on that very subject when Zetha was out of earshot. Assuming Zetha was ever out of earshot; she seemed to be everywhere on the small ship except where he’d denied her access, mostly following Selar around like a puppy, setting up petri dishes, sterilizing instruments, tidying the lab. For now—

“Where did you—?” he began, but just then Uhura’s voice interrupted him.

“Dr. McCoy’s identified our mad scientist,” she said, shimmering into being, flanked by Crusher and McCoy. “It may not help us much, but it’s a start.”

It had begun by accident, like the discovery of penicillin. Every schoolchild knows how Sir Alexander Fleming, in a bout of bachelor carelessness, went on holiday and left an uncovered dish of deadly staph bacteria lying about, only to find blue mold, no doubt migrated from someone’s unfinished lunch left equally carelessly in a wastebin, claiming its turf here and there on the surface of the dish and driving the bacteria back wherever it touched. But where Fleming’s random chance led to a cure that had saved millions, the man the Renagans knew as Cinchona had stumbled upon the power to kill as many and more.

It wasn’t what he’d wanted. Following the rout at the Medical Academy—disgraced, family ties severed, his career in shambles—he had wanted only retreat, anonymity, to disappear into the proverbial black hole and never emerge. The family had settled a small fortune on him on condition he go away, at least for a while. He wouldn’t need to work at anything. He didn’t like work; it was being pushed into it that had gotten him into trouble in the first place.

But the healer’s daughter Boralesh had attached herself to him, and, yes, the child born soon after the wedding was undeniably his—he’d done the tests to prove it, but how was he to have known the custom here?—visiting him with thoughts of retreating further, but where? Aside from the fact that Boralesh’s kin would hunt him down and drag him back, even if he could get his small ship started again, emigration inside the Zone was not the easiest thing for someone with his past, even for a Rigelian.