An ominous sky arched over Blacklion, a bouncy-looking featherbed of clouds, billows and hollows of grey extending across the Cavan-Fermanagh border.
Not that the prospect of rain would deter Oliver Usher, gently humorous walker and knowledgeable ponderer of the natural world, nor his rambling chum Ellen Graney, energetic bagger of peaks and devourer of mighty long distances.
As things turned out, we took all day to cover only a handful of miles along the Cavan Way.
Topping the road out of Blacklion, we were immediately into beautiful hilly country, with the great tent shape of Cuilcagh Mountain dominating the view ahead and the humps of the Ox Mountains rising away in the west.
In the farmyard at Ture stood the rusty cast-iron frame of a heavy old clothes mangle. "It's a good few years since I caught my fingers in that," smiled the farmer as he waved us away up the lane.
As we climbed, a wide view opened to the north over Lough Macnean Upper and its flotilla of thickly wooded islets.
Up above abandoned Corratirrim farmhouse we were out on the open hillside, walking over sedgy grass and limestone pavement dotted with wind-stunted orchids and brilliant blue tongues of milkwort.
"See these beautiful stone walls?" said Oliver. "Each stone picked specifically for its shape, to fit exactly with the others."
On over heather and bilberry to enter the coniferous plantation that masks the secrets of Co Cavan's own Burren region.
Neolithic man must have sensed an extraordinary spiritual resonance in this steep landscape of knolls and hollows, because the Burren is crowded with ancient ritual and burial sites, some swallowed by the trees, others standing in plain view.
In the heart of the forest, a slope of huge scattered rocks forms a boulder grave. The multi-ton capstone of the Calf House dolmen (a local farmer once penned his cattle within) lies tilted into the earth.
The massive, mossy slabs of the Tulaigh an Ghobain wedge tomb stand silent in a clearing. Within hailing distance lies the Giant's Grave, another wedge tomb, largely intact, 100ft long, with its five capstones still in place.
Sight-lines connected all the tombs of this prehistoric necropolis before the trees interrupted them. Nowadays one stands and stares, revolving ancient mysteries on the imagination's palate.
Other treasures lay signposted among the trees. We rocked the Rocking Stone, sat in the giant stone Druid's Chair and admired the Ring Marked Stone.
Then it was out of the forest and steeply down a slope, to Manragh and a country road between old-fashioned hayfields thick with ragged robin, docks and buttercups.
On past Legeelan crossroads with its beehive-shaped sweat-house, a primitive kill-or-cure sauna for sufferers of agues and pains. Over marshy fields scented with fragrant orchids and bog myrtle, where rare greater butterfly orchids grew 10 a penny.
And down, finally, to the Shannon Pot, where Ireland's mighty major river ran lustily forth from its wide source pool.
A last look at the dimpling water, as dark as copper, and we turned our backs to the arriving rain and headed for the car.