THE FIRST 15 MILES PASS easily as the two-lane road turns into a dirt hiking trail. We stash our bikes in the woods near the national-park gate and begin hiking. By the swab of light from our shared headlamp, we finally trip into camp just before midnight, later and more tired than expected but still enthusiastic.

I cut open the silver pouch of my first-ever MRE, revealing an oily orange sludge that is either a beef enchilada or the toxic swamp from which life first sprang. I peel the bark off a stick and twig right in. Fantastic! Genuinely spicy, and cardboard-wholesome.

For dessert, we split one of the emergency rations, vaguely biscuit-ish things the size of a gun clip, the texture of sedimentary rock, and conspicuously lacking in flavor.

"Just like the emergency rations Mom used to make," gushes Roo. Cervantes was right: Hunger really is the best sauce.

At nine the next morning, we plod toward 5,847-foot Hayden Pass, past cedars bunched in marshy meadows and through fireworks displays of spreading orange tiger lilies, drooping bluebells, and purple lupines that stretch vertically like rocket exhaust. Most beautiful of all, we are now confident that we packed well.

Roo slept comfortably in his flaccid sleeping bag and Oompa-Loompa suit, a home-sewn fleece onesie, as did I, on a foam pad trimmed to the size of a placemat. Our brand-new approach shoes have yet to cause even a hot spot and, with a bit of futzing, sorta attach to our crampons. Nutella—why didn't we think of this before?!—can double as high-SPF lip balm.

After topping out at Hayden Pass midafter-noon, we descend nine miles into camp, for a total of 21 miles and 8,000 feet of elevation change. Roo is so exhausted that before I can even erect the tent, he lays out his sleeping bag and curls up in the mossy nook of a Doug fir.