It is the sole surviving architectural fragment of what was once a Franciscan Third Order Regular house, a category of Franciscan community whose members, unlike the friars of the main order, often lived in small, relatively modest establishments integrated into local society. By 1837, Ordnance Survey mappers could still record a T-shaped, roofed building within a rectangular enclosure and label it simply "Abbey". By the time of the 1911 survey, that same structure had been reduced to an L-shaped section of walling.

The house was founded by Geoffrey O'Ferrall in the fifteenth century and dedicated to St John the Baptist. The O'Ferralls were the dominant Gaelic family of County Longford, and their patronage of a religious community here fits a broader pattern of local lordly investment in ecclesiastical life during the later medieval period. A nunnery may also have been associated with the site. Whatever its internal arrangements, the house did not survive the upheavals of the early seventeenth century intact. It was granted to Sir John Davies in 1611 and then to James Metcalfe in 1621, passing into new Protestant ownership in the decades following the Elizabethan conquest, as happened to so many religious properties across Ireland. The church still appeared on an early seventeenth-century map of Ardagh barony, but by the time of the Down Survey of 1655 to 1656, it was no longer marked on the map of Mastrim parish, suggesting it had already fallen from significance or recognition.

The enclosure surrounding the ruins measures roughly 55 metres by 38 metres internally, defined by a tree-lined earthen bank and a wide outer fosse, which is essentially a defensive or boundary ditch. In places the bank has been worn down to little more than a low scarp. A possible entrance gap about three metres wide survives in the north angle, with a linear ditch approaching from the north-west that may trace the line of an old access road, though it could equally be a post-medieval drainage feature. To the south-east, a semicircular platform with its own possible outer fosse was recorded in 1975, adding another layer of complexity to a site that repays slow, careful looking. About fifty metres to the west lies St Mary's Well, a holy well that hints at a concentration of sacred associations in this quietly unremarkable-looking patch of Longford ground.