Behind a square opening barely 0.9 metres across lay an oval chamber, 4.5 metres long and 2.5 metres wide, developed along a natural fault line visible in the cave roof. Two skulls were immediately apparent. The slab that had covered the entrance, measuring just over a metre in length, had not shifted by accident or erosion; it had been placed there deliberately, and whoever placed it had no intention of the chamber being found again.

Rescue excavations followed quickly, carried out in March and May of 1992 by archaeologist Raghnall Ó Floinn under licence 92E047. The cave floor sloped from east to west, and it was at the deepest western end, at roughly one metre in height, that the principal burials lay. Remains of five adult males were recovered in total, at least two of whom had lived into their sixties, a notably advanced age for the period. Alongside three of the burials were pottery vessels, including a bipartite bowl and a globular bowl, along with portions of two further vessels. The assemblage of accompanying objects extended to a perforated red deer antler tine, a bone toggle, a bone point, a flint blade, a flint flake, a flint arrowhead, and a flint discoidal knife. Radiocarbon dating placed all five burials in the Middle Neolithic, consistent with the pottery styles. A single bear bone recovered from the fill returned a Mesolithic date and is thought to represent earlier residual material, suggesting the cave had a longer, more complex history of use before anyone was buried there.

The cave itself no longer survives; further quarrying after the 1992 excavation removed it entirely. The quarry, which had already appeared on the 1840 Ordnance Survey six-inch map as a small working with a lime kiln to the east, and was recorded as disused by the 1897 twenty-five-inch edition, is visible in aerial orthoimages from as recently as June 2018, by which point quarrying had ceased. Two ringforts, Iron Age enclosed settlements, lie within 320 metres to the south and south-west, a reminder that this hillside attracted activity across many different periods. There is nothing to see at ground level now where the cave once opened, but the quarry scar on Annagh Hill's north-western face, cut into limestone between fifty and sixty metres above sea level, marks the approximate location of what turned out to be one of the more quietly significant Neolithic finds in the county.