In Gartan Co Donegal there is a huge stone which is kept in remembrance of St Colmcille. Long ago some Protestants were removing this stone and trying to hide it on the Catholics. When they had it some distance away a plague of black rats surrounded them so they thought they would leave the stone back again and when they did so the rats disappeared. The Protestants never interfered with the stone again.
From the Schools Collection of the 1930s, now being transcribed at Duchas.ie.