The stone records the death of Teresa Plunket on the 20th of August 1672, and its reappearance is the kind of quiet archaeological event that rarely makes headlines but carries considerable weight. The inscription had already been transcribed once before, by the antiquarian Isaac Butler on 14 June 1744, a note later extracted and published in the Journal of the Association for the Preservation of the Memorials of the Dead in Ireland, and subsequently in M. J. S. Egan's 1997 survey of Dublin graveyards. That Butler recorded it at all suggests it was accessible in the eighteenth century; how and when it became buried again is not known.

Teresa was the third daughter of William Plunket, who died in 1662. Her grandfather Luke, who died in 1636, had been granted the castle, town, lands and hereditaments of Portmarnock the year before his death, establishing the family's connection to this stretch of coastline north of Dublin. The slab, measuring 1.4 metres long and 0.55 metres wide, is oriented north to south and carved in limestone. At its head is the IHS monogram, a Christogram common on Catholic memorial stones of the period, set above a Maltese cross whose long shaft runs down through the centre of the stone. Parallel lines border the composition on either side. The inscription itself is now largely illegible except for the date, though Butler's eighteenth-century transcription preserves the full text, including the archaic spelling of "Avgust" and the use of a V in place of a U in "Plvnket." The slab was probably repositioned around 1862, when the chancel was reconfigured and a table tomb erected for John William Plunkett; there is likely a funerary vault beneath the chancel floor.

The stone was exposed by archaeologist Franc Myles of Archaeology and Built Heritage, working under licence number 22E0601 while monitoring conservation works funded by the Community Monuments Fund 2022. At the time of recording it was protected by a plastic membrane and timber boarding, with scaffolding erected overhead to allow repointing of the adjacent wall. The slab sits in the south-east corner of the chancel, near the Barnwall memorial. St. Marnock's Church is a medieval structure, and the chancel interior reflects its Victorian-era reorganisation as much as its earlier history. Anyone visiting should be aware that the stone's current condition and accessibility may change as conservation works progress.