This isn't my story but my recently deceased uncle, whom I'll call "Sean". "Sean" is my late mother's younger brother and when I was in Eire back in '94 my uncle "Sean" told me this story.
"Sean" was born in Northern Ireland, Ulster as it's also known, or in in Irish, Uliad. Uncle "Sean" was a very religious, very Catholic, man. Prayed all his life. He had always wanted to be a priest and he would've made a fine one, but my grandfather was against it and trained "Sean" to have a trade. He was a glazier. Everyone in my mother's clan had a trade, even though they were working class Catholics and the Protestants refused to hire Catholics, my grandfather made sure that they had a damned good trade to fall back upon.
Anyway, getting back to the tale. "Sean" when he was fifteen, decided to run away from home and become a priest (odd, he didn't run off to join a circus... Unless being a priest is a part of a circus, who knows?) We had a priest in the family, a man who had experiences with the supernatural, he was a well-known exorcist in Belfast, even the Prods held him in high respect. He's another story for another day, my Great uncle Father M.
"Sean" started making his way towards the Free State, as the Republic of Ireland was known in the 30's. This one night poor "Sean" found himself stranded on a cold, dark lonely back road he took for some odd reason. The night was dark and getting cold, bit of rain drizzling as he made his way along the lonely road. There was bogland all round, towering dark mountains ridges looming as the rain drifted across the moor.
"Sean" saw a shape of a building, which turned out to be an old abandoned church. There were plenty about in Ireland. I've seen a few myself when I was there. "Sean" had no choice but to try and find a way in since the door was bricked over, even where the old stained glass windows should've been were bricked over with creeping ivy over the arches. He found a way in through the old vestry, where then he found himself inside the church. In the gloom he could just make out the pews and, of course, the alter and an old worn out looking cross. He found a pew to lie upon and get a decent night sleep.
He had little food and little warmth as he shivered that night when, around maybe two in the morning, he was woken by the sound of someone saying the rosary. My uncle "Sean" slowly sat up and there, he told me, was a young priest kneeling before the altar saying the Hail Mary and Art Father but in Irish. The young man was dressed like a priest, in his dark cassock, dark hair that was slowly going bald, and palish skin. He seemed to be weeping, my uncle told me, weeping for something.
Then he heard the priest asking: "is there anyone who could help to do my Celebration of the Mass?" My uncle, who was a head altar-boy in his youth, said: "Yes, Father, I will help you." And they performed the Celebration of the Mass. The young Priest, my uncle told me, then turned, faced him and smiled, bowed his head in thanks. The young priest said the Celebration of Mass then got up and walked into the old vestry. Uncle "Sean" followed him but he was nowhere to seen, the Priest that is.
Uncle "Sean" went back to the Church and thought about his descission of becoming a priest. He decided to go home.
My uncle made his way home back to Belfast and met up with my great uncle M who was a priest. "Sean" told Great Uncle M about the young priest and found out that the young priest committed a "sin", he fell in love with a nun. They were caught having sex. She was sent off to some nunnery in France or somewhere and he was punished by the local bishop. The punishment, Great Uncle Father M said, was sentenced by repeating his penances until he was freed by someone who knew how to service the church.
My unsuspecting uncle was him. That was just about the only ghost story he'd ever told me.