Cave Falls, Yellowstone National Park.

I stood up to the bottom of my shorts in the gloriously cool waters of the Fall River, just as it prepares to leave the environs of Yellowstone National Park and wind through a short stretch of Wyoming and into Idaho, where it’s tumultuous currents finally meet the Henry’s Fork between the communities of Ashton and St. Anthony.

Here, at the base of Cave Falls, I’ve always enjoyed dependable fishing for pan-sized rainbows, with the occasional 15- to 16-incher thrown in to keep you coming back for more. And, of course, there’s the wallpaper—Cave Falls is one of the more scenic destinations in the park, and casting a fly here is a privilege afforded to every American public landowner (that’s you, just in case you were wondering).

I managed to fool a few scrappy fish with a fat, foam hopper pattern, but the action was sporadic. And, even with the foam fly designed more for my eyes than for those of the trout below, the turbid water fresh off a tumble over the falls was quick to drown my bug.

I decided to go deep, and rather than simply drop a nymph under the hopper, I went for the full-on Thingamabobber in bright pink. For the dropper, I chose a big size 12 Prince Nymph, a classic attractor that doesn’t really imitate one bug in particularl, but does a good job exhibiting the attributes of a number of aquatic bugs.

And, of course, there’s the peacock herl used to tie this fly—this material is one of the best to use when you’re simply trying to get the attention of trout. It’s “insect green” appeal just seems to work.

In a matter of minutes, I was back in the Cave Falls groove—fish were coming to hand at a quick clip, and I managed to catch my largest Fall River fish ever—a 17-inch rainbow that took the nymph and then rocketed from the water and put on an aerial display I won’t soon forget.

Then, as my luck would have it, I broke the fly off on a subsurface rock, and realized, as I searched through my nymph box, that I’d used my last one.

Not having a dozen Prince Nymphs in your fly box? That’s a cardinal sin for any angler who likes to chase trout in off-the-beaten path destinations.

I’m making up for it this week at the vise.