There once was a king of Ulster in Celtic lands named Connacher, and he had heard of a woman named Deirdre, a maiden said to be so beautiful that Connacher had to see for himself if the stories were true. So he up and traveled with his soldiers to the land of this maiden, and when he found her home in the forest, he laid eyes upon her and saw that indeed she was the fairest woman he had ever seen. And he knew he had to have her. So he seized her and brought her back to his castle to wed him, but Deirdre pleaded that she be allowed a year and a day respite, and at the end of that time, she would marry him. Connacher agreed.
Time passed, and one day while out roaming the fields of Ulster, Deirdre saw a young man named Naois who was traveling with his two brothers Allen and Arden. At the sound of his voice, she fell in love with him, and he with her, and fearful of the king’s wrath, they traveled into Scotland, there to dwell in safety and joy. But the king discovered their hiding place and set a trap. He sent Ferchar Mac Ro and his three sons to convey the king’s pardon and to invite them back to his realm for a great feast. However, when Mac Ro and his sons reached the home in Alba and saw fair Deirdre and the beauty of her love for Naois, they swore to protect them if they decided to return to Ulster and face King Connacher.
And so they traveled to Ulster, and Connacher sent out 300 warriors to kill Naois and his brothers, but the sons of Mac Ro stood between them and would not let through a single warrior. When all the warriors lay dead on the field, Naois and Deirdre were still safe and sound. But they knew then that they could not trust the promises of the king, so the lovers fled with Allen and Arden, journeying back to Alba.
King Connacher, desperate and enraged, now called on his mighty druid to use magic to stop them from escaping his clutches. The druid conjured a dark forest to halt the travelers, but they courageously made their way through unharmed. Then the druid caused the grassy plain to flood with a gray and shallow sea, but still the brothers continued on, wading through the water unscathed with Naois carrying Deirdre on his shoulders. Connacher was furious. He ordered his druid to kill them, and the wizard turned the waters into stones as sharp as swords and as poisonous as snakes.
Arden was the first to fail, and Naois grabbed him and placed his brother on his own shoulder beside Deirdre, and there Arden died. But then Allen too succumbed to the blades and the poison, and as he breathed his last, Naois lifted him onto his other shoulder. And even as the poison coursed through his own blood, Naois would not stop. He refused to leave his beloved in the midst of such mortal danger. So he continued on until he reached Alba and the shores of Loch Ness, and there he collapsed and perished.
A wide grave was dug for the three brothers, but Deirdre was inconsolable. Standing beside the open grave, she said to her beloved, “If the dead had any sense to feel, Ye would have made a place for Deirdre.” At her lament, the bodies did indeed move aside, making a place for her, and so she lay down beside her beloved and died.
Connacher in his jealousy had the grave dug up and the bodies of the brothers moved to the other side of the loch. But even then, a fir tree grew from the grave of Naois and another fir tree grew from the grave of Deirdre, and a shoot from each tree grew over the loch and twined together. And each time Connacher tried to cut down the shoots, they again grew out and embraced one another over the mournful loch.
[There are various versions of this tale, but this is the one that clings to my thoughts.]