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.
MAP: OS of Ireland 1:50,000 Discovery Sheet 26; map/ instructions downloadable at discoverireland.ie/walking or irishtrails.ie.
TRAVEL: (2 cars): N16 or A4 to Blacklion; N16 towards Manorhamilton. On outskirts of Blacklion, left on R206.
Follow 'Glangevlin, Cavan, Shannon Pot' for 5 miles (8km); then left (brown 'Shannon Pot' sign) to Shannon Pot car park. Leave one car; return in the other to Blacklion.
WALK DIRECTIONS: At crossroads, turn up beside Enzo's ('Cavan Way'/CW). In 3 miles (1km), left (CW yellow arrow and 'walking man' symbol) along lane past Ture, up to Corratirrim. Pass house; bear right up open ground with wall on right (CW).
Nearing forestry, right over stile (CW); right along forest edge; left over stile (CW). Woodland path to forest road; left (CW, 'Burren').
Follow CW past 'Lost Valley' fingerpost; past Boulder Grave and Ghobain's Mound (signed left and right -- both worth a detour); to Calf House dolmen on right.
Left here (CW) on grassy track, following Giant's Leap wedge tomb/CW, to pass wedge tomb, Druid's Chair, Ring Marked Stone (all signed). CW turns left over wall; steeply down slope (CWs). Just before white house, bear right (CW) to road at Manragh.
Follow road to Legeelan crossroads (sweathouse on right, 100m up lane opposite). Left at Legeelan crossroads; in 300m pass church; ignore 'Garvagh Lake' to left and keep ahead for 1 mile, passing Mullaghboy turn on left.
Just after rough lane ('West Cavan Gun Club' notice) on left, right over stile. Follow CWs over boggy meadows, through forestry and on to car park. Left to visit Shannon Pot; return to car park.
LENGTH: 8½ miles with detours/14km. Allow 4-5 hours.
CONDITIONS: Parts are very boggy; waterproof footwear advised.
DON'T MISS: Wonderful flowery uplands above Corratirrim; fragrant and greater butterfly orchids (June onwards) between Mullaghboy and Shannon Pot; Megalithic tombs in the Burren Forest.
REFRESHMENTS: Macnean House, Blacklion (dinner Wednesday-Sunday, lunch Sunday). Try their ballotine of rabbit or braised shoulder of venison -- tiptop local ingredients and cooking. Tel: 071 985 3022; nevenmaguire.com.
BEST PICNIC SPOT: On the slopes above either Corratirrim or Manragh.
ACCOMMODATION: Clancys of Glenfarne (071 985 3116; clancysofglenfarne.com) -- very welcoming and helpful. Two nights' double B&B, dinner and packed lunches for €119pp.
GUIDED WALKS: Oliver Usher. Tel: 086 170 6767; email email@example.com.
CAVAN TIC: Tel: 049 433 1942; cavantourism.com.