The most conspicuous of these is the world-renowned Woods Hole Oceanographic Institution. Nearby, in a vintage brick-and-granite edifice, is the Marine Biological Laboratory, whose research programs and library of nearly two hundred thousand volumes attract scholars from around the globe. Within walking distance of the MBL is the National Marine Fisheries aquarium. On the outskirts of the village are the U.S. Geological Survey and dozens of sea education institutions and private companies that produce the high-tech underwater gadgets used by ocean scientists the world over.

A breeze was coming off the harbor from the direction of the Elizabeth Islands. Trout paused on the tiny drawbridgejthat separates Eel Pond and Great Harbor and he filled his lungs with salty air, thinking that there must be some truth to the gill-closing story. He could actually breathe again. /

Trout was the son of a local fisherman and his wife, and his family still owned the low-slung Cape Cod cottage where he had been raised. His intellectual home was the Oceanographic Institution. As a boy he used to run errands for some of the scientists who worked at the institution and it was at their encouragement that he had specialized in deep-ocean geology, a move that would bring him eventually to NUMA and its Special Assignments Team.

Within hours of their arrival, Paul had checked on his house, touched base with several relatives and stopped off for lunch with Gamay at a local watering hole where he knew everyone at the bar. Then he began to make the rounds. He was visiting the Institution's Deep Submergence Lab where an old colleague was bringing him

up-to-date on the latest in autonomous underwater vehicles, when the phone rang.

"It's for you," his colleague said, handing Trout the phone. A voice boomed on the line. "Hello, Trout. This is Sam Osborne. Heard down at the post office that you were back in town. How are you and your lovely wife?"

Osborne was a phycologist, one of the world's foremost experts in the science of algology, or the study of algae. After years of teaching, he still talked in a range that was two or three decibels above that of a normal human being.

Trout didn't bother asking how Osborne had tracked him down. It was impossible to keep anything secret in a village the size of Woods Hole. "We're fine, thank you. Nice of you to give me a call, Dr. Osborne."

Osborne cleared his throat. "Weller actually I wasn't calling you. I wanted to speak to your wife."

Trout smiled. "I don't blame you for that. Gamay is much prettier than I am."

He handed the phone to his wife. Gamay Morgan-Trout was an attractive woman, not gorgeous or overly sexy, but appealing to most men. She had a flashing smile with a slight gap in her upper teeth like the model-actress Lauren Hutton. She was tall, five feet ten, and 135 pounds, slim for her height. Her hair, which was long and generally worn swirled, was dark red, the reason her father, a wine connoisseur, had named her after the grape of Beaujolais.

More open and vivacious than her husband, she worked well with men, a talent that went back to her tomboy days in Wisconsin. Her father was a successful developer who had encouraged her to compete with men, teaching her to sail and shoot skeet. She was an expert diver and marksman.

Gamay listened for a moment, and then said, "We'll be right over."

Hanging up, she said, "Dr. Osborne has asked us to come by the MBL. He says it's urgent."

"Everything is urgent to Sam," Paul said.

"Now, now. You needn't be snide just because he wanted to talk to me."

"I don't have a snide bone in my body," Paul said, linking arms with Gamay.

He bid good-bye to his colleague in the Submergence Lab and he and Gamay set off along Water Street. A few minutes later, they were climbing the wide stone steps at the Lillie Research Building, where they went through an arched doorway into a quiet lobby.

Dr. Osborne was waiting for them just inside. He pumped Paul's hand and embraced Gamay, whom he'd had as a student when she was studying marine biology at the Scripps Institute of Oceanography in California. Osborne was in his mid-fifties, and his receding, curly white hair seemed to be slipping off the back of his skull. He had a big-boned physique and large workman's hands that looked more suitable for handling a pickax than the delicate strands of marine vegetation that were his specialty.

"Thanks for coming over," he said. "I hope that This is no imposition."

"None at all," Gamay said sweetly. "Always a pleasure to see you."

"You may not think so when you hear what I have to tell you," Osborne said with an enigmatic smile.

Without further explanation, he led them to his office. Although the MBL was known all over the world for its research facilities and library, the Lillie Building lab was an unprepossessing place. Exposed pipes ran along the ceilings, the doors lining the hallways were of dark wood with pebbled glass panels, and in general it looked exactly like what it was, a venerable old lab building.

Osborne ushered the Trouts into his office. Gamay had remembered Osborne as fanatically neat and organized, bordering on the anal, and she saw that he hadn't changed. Where many professors of his stature surrounded themselves with piles of paper and reports, his office consisted of a computer table and chair and a couple of folding chairs for visitors. His only luxury was a tea maker, which he had picked up in Japan.

He poured three cups of green tea and after a brief exchange of pleasantries, he said, "Pardon me for being so brusque, but time is short, so I'll get right to the point." He leaned back in his chair, tented his fingers and said to Gamay, "As a marine biologist, you're acquainted with Caulerpa taxi folia

Gamay had received a degree in marine archaeology from the University of North Carolina before changing her field of interest and enrolling at Scripps, where she'd attained a doctorate in marine biology. Gamay smiled inwardly as she remembered being a student in Osborne's class. He typically asked questions in the form of a statement. "Caulerpa is an alga that's native to the tropics, although it's often seen in home aquariums."

"Correct. And you know that the cold-water strain that thrives so well in aquaria has become a major problem in certain coastal areas?" Gamay nodded. "Killer seaweed. It's destroyed large expanses of the seabed in the Mediterranean and has spread to other places as well. It's a strain of a tropical alga. Tropical algae don't normally live in cold water, but this strain has adapted. It could spread anywhere in the world."

Osborne turned to Paul. "The weed we're talking about was inadvertently released into the water beneath the Oceanographic Museum of Monaco in 1984. Since then it has spread to thirty thousand hectares in the coastal floor off six Mediterranean countries, and it's a problem off Australia and San Diego. It spreads like wildfire. The problem goes beyond speed. The Caulerpa colonies are extremely invasive The weed spreads out with runners and forms a dense green carpet that crowds out other flora and fauna, depriving plants and animals of sunlight and oxygen. Its presence destroys the base of the marine food web, damages native species with devastating consequences for ecosystems."

"Isn't there any way to fight this stuff?"

"In San Diego, they've had some success using tarpaulins to quarantine patches of weed, while pumping chlorine into the water and the mud that anchors the plants. This technique would be useless with a widespread infestation. There has been an effort to educate aquarium dealers who sell Caulerpa or deal in rocks that might be contaminated with organisms."