The site was called Bethlehem, and the name alone suggests something of its founders' self-understanding: a place of refuge, deliberately obscure, built into a marsh so wet that water seeped up through the floor during rainy weather. A first-hand account, written in Irish by one of the nuns who lived there, Mother Mary Bonaventure Browne, describes the ground-level cells, the leaking roof, and the community's deliberate withdrawal from towns and cities. The nuns brewed, baked, hauled turf, and received materials for construction through the grille. Their number eventually reached sixty. Among those who came to observe this austere life was Elizabeth Rodes, third wife of Lord Wentworth, then Deputy of Ireland.

The community had arrived at Bethlehem by a circuitous route. Forced out of their Dublin house towards the close of 1630, the nuns were sheltered by sympathetic lay supporters before a modest dwelling was built for them on the Lough Ree promontory. The convent was formally established in 1631, with the abbess recorded by Sir Henry Piers in 1682 as a daughter of Sir Edmund Tuit. It survived barely a decade before being destroyed in 1642. The attack was carried out by soldiers later identified by Piers as acting under a Captain Bertie, brother to the Earl of Lindsey, who had commanded Royalist forces at the Battle of Edgehill. Warning reached the sisters in time; they escaped by boat onto the lake, leaving behind most of their belongings and even their habits in the urgency of the flight. The attackers occupied the empty convent for three days and nights, mocking its altars and ornaments, before burning it. A petition submitted to the Supreme Council in 1647 by the survivors, then numbering twenty-four and sheltering in the ruined town of Athlone, named Lord Ranelagh as the principal responsible party. The Council's response, referring to the community as "these poor damosells", proposed an allowance of £200 a year to be drawn partly from Ranelagh's own estate. Meanwhile the island where the nuns had taken refuge on Lough Ree, finding shelter in a pre-existing medieval church, became known as Nun's Island. Mother Mary Bonaventure Browne herself was among a group of fourteen sent to found a new convent in Galway in 1642. After Galway's surrender to Cromwellian forces in 1652, she went into exile in Spain, where she died sometime in the early 1690s. The narrative she wrote there, covering the Poor Clares in Ireland from 1629 to 1670, survives in English translation at the Poor Clare convent in Galway; the original Irish text has been lost.