It was lifted stone by stone from Friars Island in the River Shannon and rebuilt on dry land in 1930, rescued not by any heritage campaign but by an engineering project. The construction of the Ardnacrusha hydroelectric power station by the ESB raised the waters of the Shannon and swallowed the island entirely. The church came with it to the mainland, or at least most of it did; the island itself is now somewhere beneath the river.

The building is dedicated to St. Molua of Kyle, a monk associated with Clonfertmulloe in County Laois who died in 609 and whose feast day falls on the 4th of August. What survives is a multi-period structure: a nave dating to the 10th or 11th century, built from large uncoursed cyclopean sandstone blocks, and a 12th-century chancel added later in more neatly squared stonework of smaller dimensions. When the church was being dismantled for its move, the two phases became physically legible; external wall plaster was found between the two cells, confirming that the nave had stood as a finished, plastered structure before the chancel was appended. The chancel retains a round-headed east window with a stepped sill-stone and an unusual flat-headed doorway in the south wall. The chancel arch itself has projecting jamb-stones that do not sit flush with the arch, an oddity that survives intact. Excavations on Friars Island before the removal uncovered that the church had originally been built on a raised stone platform, possibly enclosed by a cashel, which is a dry-stone enclosure wall typical of early Irish ecclesiastical sites. A second stone platform lay to the south, and eleven skeletons were found beneath or close to the foundations of the north wall. The island also has a brief, oblique mention in military history: a Parliamentary army officer's diary entry for 24 May 1650 describes soldiers occupying a small island in the Shannon near Killaloe where they found ruins of a stone building and posted a guard, the description matching Friars Island closely enough that the ruins he noted were almost certainly St. Molua's church.