Based on my conversation with author Denis O’Neill, I might think twice about going for a nature hike with him. The temptation to veer from the main path to explore intriguing side trails would be too great.

Metaphorically speaking, the main path in this case is talking to him about his new wilderness thriller, Canis Dirus, which Kirkus Reviews pitches as “Arthur Conan Doyle’s The Lost World in California.” But as our conversation proceeds, it reveals “Wait, what?” digressions that demand exploring. For example, his father wrote for the iconic golden age of radio series Fibber McGee and Molly and was friends with Theodore Geisel, aka Dr. Seuss; O’Neill himself was once part of a folk-singing duo that opened for Steve Goodman and earned the praise of Gordon Lightfoot’s bass player; and his Dartmouth hockey jersey made a cameo appearance in the film Love Story.

But back to Canis Dirus, which combines O’Neill’s keen eye for nature with a screenwriter’s cinematic savvy for propulsively paced scenes of adventure, action, and terror. Think: Jaws meets Jurassic Park. The story is set in Yosemite National Park, where an earthquake frees a pack of aptly named dire wolves from their subterranean confinement after a thousand years. Park ranger Axten Raymond and his fiancee, Petra Stahl, who knows her way around a rock face, have no clue as to the ancient horror they are up against when a backpacker disappears.

Kirkus praises the book’s “sheer amount of breathtaking, heart-stopping action and adventure, which creates a relentlessly paced, adrenaline-inducing thrill ride that will have readers on the edges of their seats until the very end.”

O’Neill is no stranger to writing about nature’s wilder side. He wrote the screenplay for The River Wild, which cast Meryl Streep as an action hero. “I have a book of fishing stories, Jim & I,” he says. “They are more idyllic and describe the beauty, joy, and peace of nature. But if you’re trying to capture a reader’s interest, it’s good to throw in a little jeopardy.”

The book’s initial scene of violence establishes the danger that reverberates throughout, like the victim’s echoing scream:

He emerges from the tent and stands for a moment in his unlaced boots and long johns, enjoying the glorious heavens. His breath billows before him in the chill night air. Duane wallows in the splendor, happy to be alive and out of L.A., unaware he’s being watched by someone or something, with incredible infrared-like, nightvision…The stalker closes in, silently. Closer...closer. The hair on Duane’s neck suddenly bristles. His body tightens. You don’t stand on the hallowed Killing Ground without possessing animal instincts. He senses something behind him. Part of him wishes it was his imagination, or would simply go away if it were real. His sphincter tightens, sending more urgent information. Duane turns slowly.

O’Neill himself grew up with his three brothers, basking in nature’s more idyllic graces. A brook near their home in Green Farms, Connecticut, offered fishing in the summer and a ready-made skinny hockey rink in the winter. “It informed my storytelling,” O’Neill says, “being in nature with all the glory and precariousness.”

O’Neill’s brothers all became lawyers; he got “the storytelling gene,” he says, from his father, Charles, whose short stories were published in the New Yorker and whose Guggenheim grants enabled him to write two works of historical fiction: Wild Train: The Story of the Andrews’ Raiders and Morning Time.

Following WWII, in which O’Neill’s father served in the OSS along with the woman he would marry (and who O’Neill credits with inspiring his strong female characters), his father moved to Hollywood, where he worked as a screenwriter. “He had great friends, including Ted Geisel,” O’Neill says. “Both were editors at the Dartmouth Jack-O-Lantern, the college’s humor magazine. My house was filled with smart writers. The conversation was opinionated, sharp elbowed, funny, and forceful. [My father’s] Rat Pack included actor Robert Ryan and directors Elia Kazan and Jean Renoir, with whom he collaborated on an unproduced screenplay.” O’Neill found it when he was named the executor of his father’s literary estate after his death in 1997. “I took the script to the Writers Guild,” he says with a laugh. “They were giddy.”

O’Neill himself moved to Hollywood with a dream of selling something quickly and moving back to Boston. But it’s like the Eagles song, he says: You can never leave.

River Wild was his 10th script and the first one he sold. Canis Dirus originated as an unproduced spec script. There were three legs to this story table, he says: The first was his own experience backpacking in the Sierra’s high country. “I started getting immersed in that world. I liked the look and the danger of it. I knew there were actual critters you could get in trouble with.” The second leg was an animated screenplay he was hired to write for Ted Turner about a project to return wolves to Yellowstone National Park. The third was a visit with his children to the La Brea Tar Pits. “Turns out,” he says, “the animal with the most bone remains were dire wolves.”

As with Jurassic Park, the challenge for him was to make his fantastic concept of a surviving pack of ancient dire wolves credible. “The quality of the storytelling has to carry the reader,” he explains. “Once they accept your concept, you’re over that hump. Then you establish your story beats in a way that is compelling and overlay your characters and descriptions of nature.”

He jokingly offers an irresistible tagline for the book: “They’re back and they’re hungry.”

While supplying the book’s thrills was paramount, O’Neill, a self-described “big environmentalist,” does hope that readers take away an appreciation for nature’s beauty and vulnerability. “These beautiful places still exist in the world and need our protection,” he says.

O’Neill is savvy to the ways of Hollywood, and it informed the ending of his book. Without giving too much away, let’s just say it falls under the classic movie tradition of “The end?” “The Hollywood model these days is that a stand-alone movie is not as valuable or attractive to studios as a big special effects movie that can be spun off into sequels,” he says. “That’s why I wrote that tease at the end. It’s an awareness of the business model.”

Donald Liebenson is a Chicago-based writer.