The scenic comedy “A Walk in the Woods” (Broad Green)  — adapted from Bill Bryson’s 1998 memoir  — treads both sides of the moral divide simultaneously, making his expedition suitable only for discerning adults.

The film focuses on a pair of mildly cantankerous older men — travel author Bill Bryson (Robert Redford) and loveable rogue Stephen Katz (Nick Nolte).

Bill, chafing at semiretirement and seeking a remedy for his long-standing writer’s block, decides to hike the 2,200-mile-long Appalachian Trail.

Bill’s eminently sensible wife Catherine (Emma Thompson) objects vigorously. Though he remains resolute, Bill does at least yield to Catherine’s insistence that he include a companion on the trip.

But the only volunteer Bill can find to accompany him turns out to be Stephen, a figure from his distant past with whom Bill — at least partly by choice — has long been out of touch.

As domesticated Bill and his rolling stone of a sidekick lumber through the forest, they pass the time comparing notes on life.

A surfeit of the pals’ dialogue deals with sexuality — including the humorously remembered bedroom escapades of their shared youth. And the frivolous tone of the script invites viewers to regard physical intimacy, at last among singles, as little more than a form of entertainment.

Marital fidelity gets a somewhat more sober treatment. But even events turning on this topic are dealt with ambiguously.

While one sequence celebrates faithfulness in the face of temptation, another winks at a potentially adulterous dalliance. The moral significance of this potential encounter is sloughed off on the dubious grounds that the randy behavior of fat people is too ridiculous to be taken seriously.

All this detracts from what is, in other respects, a generally pleasant, though excessively talky, excursion through a series of landscapes that vary from the soothing to the magnificent.

The film contains defective values, including an ambivalent attitude toward adultery, a non-graphic scene of aberrant sexual activity, a glimpse of partial rear nudity, much off-color humor, numerous uses of profanity and frequent rough and crude language. (L, R).