Scattered across the waters of Lough Key in County Roscommon lie dozens of small islands. On one stands the romantic ruin of McDermott’s Castle, its ivy-clad walls rising above the trees. To some, it is a postcard view. To others, it is a place of heartbreak — the setting for one of Ireland’s most enduring love stories.

For centuries, these islands were the stronghold of the McDermotts of Moylurg. Castle Island was their fortress, its waters both lifeline and defence. Yet of all the tales tied to their name, none is remembered more tenderly than the tragic story of Úna Bhán MacDermot and Tomás Láidir Costello — “Strong Thomas.”

Úna fell in love with Tomás, from a rival family. Her father forbade the match and confined her to Castle Island. From the mainland, Tomás could see the place where she was held. He tried to swim across to her, but the lough was merciless. Despite his strength, its waters claimed him.

When word of his death reached Úna, her grief was overwhelming. Within weeks, she too had died. Folklore says they were laid to rest side by side on Trinity Island, where two trees once grew from their graves and slowly entwined — united in death as they had been denied in life. The trees are long gone, but the legend endures.

And so, many say, do the ghosts.

On still evenings, a figure in white is seen walking the shoreline, eyes fixed across the lake. Boatmen whisper of a woman’s voice carried on the wind, though no one is there. Fishermen tell of sudden, icy chills, as if an unseen hand brushed against them — or rested on their shoulder.

Visitors to Trinity Island sometimes glimpse a pale figure gliding among the graves, vanishing when approached. And in the ruins of McDermott’s Castle, rebuilt in the 19th century as a romantic folly, many speak of an unseen presence watching from the shadows.