Rolling Back The River by Paul Guernsey

While fly-fishing on a remote river in southern Argentina, a veteran outdoor writer from Maine finds himself swept into a cascade of bizarre events, all connected to an enigmatic, billionaire environmentalist and his cosmopolitan twin nieces.

Vincent Mapp, former adventure-traveling editor-in-chief for an international fly-fishing magazine, now leads a life centered around teaching at a small Maine environmental college and obsessively fishing his home waters for just about anything that swims. But after his wife of many years abruptly upends his world by ditching him for someone who doesn’t fish all the time, Vincent decides to accept one last far-flung assignment as a fly-fishing journalist, and he heads off to Patagonia with the goal of catching some of the few remaining, fast disappearing, Argentinian landlocked salmon—all of which are descended from fish originally introduced to Argentina from Maine. Even at the literal end of the earth, however, and exploring an enchanted landscape of devastating beauty, Vincent finds himself unable to avoid conflict. He arrives at an isolated ranch on the Perca River just as a mysterious predator has begun attacking pets and livestock—and it’s not long before he experiences his own terrifying nighttime run-in with the creature. He also discovers that the reclusive American owner of an adjacent ranch—multi-billionaire wildlife conservationist and avid fly-angler J.T. Allman—has been commissioning some unsettling environmental experiments on his vast property. One serious complication in Vincent’s attempts to get to the bottom of all the strangeness: Allman holds a simmering 20-year-old grudge against him for events connected to his time as a magazine editor. Turbulent waters become increasing treacherous after Allman’s cultured, equestrian, and attractive twin nieces, unaware of their elderly uncle’s animosity toward Vincent, invite him to a bizarre festival on the grounds of the Allman estate. Through it all, Vincent and his faithful fishing guide, Sancho Nelson, try very hard to catch some salmon.