The stone, measuring roughly 40 by 30 centimetres, reads something close to 'X MARGARET O'DINIGHEN, EJUS 1666, VXOR, HIC JACET', which translates loosely as 'here lies Margaret O'Dinighen, wife, 1666'. The X before her name has puzzled scholars; it may have been intended to link the inscription to a companion stone, perhaps her husband's, or it may simply have served as a stonemason's mark when the two were separated. That a memorial slab ended up as building material, turned to face outwards into the doorway, says something about the long and layered history of this site.

The ruined church at Rattoo sits in a graveyard enclosed by a nineteenth-century stone wall, immediately south-east of the well-preserved Rattoo round tower, the tall cylindrical structure of early medieval monastic Ireland that still dominates this part of north Kerry. The church itself is a small rectangular building, roughly 10 by 5.5 metres internally, constructed from an eclectic mix of yellow and pink sandstone with some limestone and shale. Its history is difficult to untangle. It is generally dated to the fifteenth century, though earlier features are clearly visible, including the west doorway, which presents a pointed arch on its outer face but is covered by a flat lintel on the interior, a combination that suggests earlier work was incorporated or adapted. The east window, a narrow twin-light ogee-headed opening with hollow spandrels, has lost its central mullion, and the dressed stones set into its surrounds indicate it was inserted rather than original to the build. The church is thought to be the successor of a pre-Norman foundation, though nothing is known of its early history with any certainty. By 1597, when a grant of the tithes of Rattoo was made to a George Isham, it was already noted that those tithes had previously belonged to the local hospital or abbey.

The north wall contains some unusually large stones in the external masonry that may be the remnants of an even earlier structure, and footings projecting from the south-west corner point to a building that once stood adjacent. The east end of the interior has been built up with modern vaulting, which complicates any reading of the original fabric. It is the kind of place where the building itself resists a single date or a single story, each wall offering a slightly different answer.