HIS IS IT, SIR.” The lead geologist double-checked her GPS and overlaid its image with a satellite-based graph. “Satellite and radar confirm it. This stream leads to the underground source that the subjects get their water from.”

“I hope you’re right,” Dr. Gunther-Hagen said icily. He was irritated at the Cirque du Soleil blunder, tired from the late-hour flight, and altogether eager for some progress in this project. “Your performance up till now has been pathetic. Be glad I’m somewhat more forgiving than Mr. Chu.”

The geologist swallowed and rechecked her instruments with fingers that trembled slightly. “No, this is it,” she said, trying to make her voice strong. “I’m positive.”

“Okay, then,” said Dr. Gunther-Hagen. “Release the reactant.”

Another agent opened a foam cooler. A fog of dry ice swirled around them like early-morning mist. He carefully pulled on heavy gloves that protected him from fingertip to elbow. Following that, a gas mask covered his face. The others moved away to stand upwind. The agent carefully removed a test tube from the dry ice with tongs. He uncapped it, and after a moment’s hesitation, tipped the test tube so its pale pink liquid flowed into the thin mountain stream.

“Of course, this will affect everything it comes into contact with,” he murmured, praying that Dr. GuntherHagen knew what he was doing.

“Not necessarily,” said Dr. Gunther-Hagen. “It’s been specialized to bind only to certain receptors. These mutants have them; not many other species do.”

The team was silent as the reactant blended invisibly with the crystal-clear stream. Within thirty minutes, it would infiltrate the natural water reservoir that served the flock’s house.

Dr. Gunther-Hagen could barely contain his excitement. Now the real experiments would start.