That modest emergence gave little indication of what lay beneath: a subrectangular slab with a gently rounded top, its broad western face covered almost entirely by an intricate incised design of a cross of arcs set within a double circle, the whole composition resting on a symmetrical arrangement of paired back-to-back spirals, flanked by two small Maltese crosses, each contained within its own circle. A trace of plait-like ornament fills the narrow band between the upper arc and the stone's top edge. It is a remarkably dense piece of early medieval carving, compressed into a single face as though the maker was determined to leave no space unaccounted for.

The platform on which the slab originally stood appears to have been a site of some ritual or communal significance. Henry's excavation found that the slab had been enclosed on its eastern side by a low semi-circular wall or bank of loose stones and dark earth, and at the base of the cross, within the arc of that wall, lay a deposit of burnt clay, ashes, and shells. A companion cross-slab, a separate stone, still stands in situ on the eastern perimeter of the same platform. The removed slab, designated National Monument no. 379 and now held by the National Museum of Ireland, left behind a site that remains only partially interpreted. Inishkea North is one of the Inishkea Islands off the coast of County Mayo, a location that lends the find a particular remoteness; the platform and its remaining stone sit on an island that has been uninhabited since the early twentieth century.