Deep in the untamed heart of Idaho lies the Frank Church - River of No Return Wilderness, part of the largest roadless area left in the lower 48 States. Named in honor of Idaho Senator Frank Church, and for the rugged Salmon River that flows through it, the vast 2.5 million-acre wilderness is larger than Yellowstone, yet most people have never even heard of it. Defined by deep canyons, and mountain forests, it is a perfect habitat for abundant animal life, including wolves that are being restored to the area after an absence of 50 years. This is the place where a young couple, Isaac and Bjornen Babcock, choose to spend a year-long honeymoon. But what begins as a romantic adventure becomes something of much greater consequence for both of them – a story that will change their lives.

NATURE'S RIVER OF NO RETURN, premieres Wednesday, April 18, 2012, at 8 p.m. (ET) on PBS (check local listings). After broadcast, the series will stream online at pbs.org/nature.

Celebrating its 30th season, Nature is a production of THIRTEEN in association with WNET, the parent company of THIRTEEN and WLIW21, New York's public television stations and operator of NJTV. For nearly 50 years, WNET has been producing and broadcasting national and local documentaries and other programs for the New York community.

Working with the Nez Perce Tribe in Central Idaho, wolf biologist Isaac Babcock was part of the wolf reintroduction program organized in the area. His 13-year experience with the wolves there led to his desire to share the raw beauty of the untamed wilderness and the wolves with his new wife, Bjornen. It was unquestionably a wild idea for a honeymoon.

Once occupied by miners and homesteaders, the River of No Return Wilderness was reclaimed by nature after it was designated a federally-protected wilderness in 1980. Otters and elk, deer and coyotes, blue birds, bighorn sheep and the newly-restored wolves thrive here. Nine packs of wolves roam freely through the wilderness, each pack dependent on family cooperatively raising young and hunting together to survive. Isaac and Bjornen spend days waiting and watching for their chance to observe the wolves and are rewarded by glimpses of parents and their pups, by deer intently and gracefully avoiding wolves in a golden meadow, and by a young wolf curious to know more about these two human interlopers, coming within 30 feet before circling and passing by.

For all the species in the wilderness, survival depends on cooperation and safety in numbers. A lost young buck or a solitary ram injured while fighting for a mate can become easy prey for the wolves. Any carcass abandoned by the wolves would feed the coyotes and other scavengers.

One injured and isolated elk defies the odds as Isaac and Bjornen look on. As a pack of wolves circle, another elk inexplicably arrives to defend her, and all the rules of survival of the fittest in the wild go out the window in a remarkable display of courage and compassion. This selfless act is an inspiration to the young couple facing the elements on their own, taking care of one another in the face of hardship.

Bjornen's hardships in the wild are complicated by a recent diagnosis of rheumatoid arthritis. She is plagued by swelling and pain in her joints, causing difficulty walking and sleeping, all symptoms that would be hard enough to manage in a standard urban setting. Add heavy backpacks and strenuous hikes up the sides of mountains and through tangled forest undergrowth to the equation and the level of difficulty rises significantly. Still, the splendors of nature comfort her and offer their kindred spirits for her to reflect upon. She chooses to stay.