SPOILER: Plot details or story follow.
Dinty was the cabin boy for a ship called the Belle of Erin. His captain asks him to go to a nearby island, Trilli, and chop down a pine tree to take back home. Unfortunately, Dinty releases Old Mag the Hag, who has been buried underneath the tree, and causes a storm so bad that Dinty is unable to find the Belle of Erin.
Dinty's day brightens up when he stumbles upon a cave filled with gold. There he meets Blarney, the head of the Kilakillarney clan, who initially mistakes him for a common thief. After Dinty, flustered, explains himself to the leprechaun, Blarney invites him for tea and tells him the story of Mag the Hag and Blarney's own falling-out with the rest of the Kilakillarney clan. Dinty is fascinated, but, at the same time, criticizes Blarney's choice to abandon the family.
Later, Blarney realizes that his tea was bewitched by Mag the Hag and nearly gives his gold to her when she arrives on the scene. He then decides to give the gold to an uncomfortable and frantic Dinty. Hoping that the storm has cleared up, Dinty ventures to the shore and is saddened to find that the Belle of Erin has washed away in the midst of the storm. Suddenly, though, he hears a girl sobbing. This girl introduces herself as Colleen, a survivor of a shipwreck who has washed ashore. Dinty comforts her and takes her to a campfire, where they talk about the leprechauns and their gold.
Colleen suggests Dinty have the leprechauns build them a ship to take them to Ireland and share the gold with "the folks in Killarney". He gleefully agrees and breaks out into song (Christmas in Killarney). In this musical number, which is a daydream sequence about the citizens of Killarney, the leprechauns, and Dinty and Colleen themselves having a Christmas party and reveling in their gold, it is implied that Dinty is falling in love with Colleen, whom he kisses and dances with.
Back in reality, Dinty gives the gold to Colleen, who begins laughing wickedly-- and transforms into Mag the Hag before his very eyes. Before Dinty can take it back, Mag casts a spell on him, "The Sleep of a Hundred Christmases", that causes him to become unconscious. Blarney, who has been watching from behind a nearby rock, is saddened.
In the morning, the leprechauns gather by Dinty's body and mourns his perceived death. Blarney and his wife, Faye, reunite and begin to mend their marriage during this time. Much to their amazement, they are soon approached by Dinty, who, having not been dead after all, says that he "was guided by a light from a love that never died." Not much later, the group sees Mag the Hag turn to tears and get washed away forever in the ocean. When the Belle of Erin returns to the island to find Dinty, the leprechauns-- and their gold-- board the Ireland-bound ship with him.
- Dinty notably bears a strong resemblance to Jack Frost's human alter ego, "Jack Snip". The two are also some of the only Rankin/Bass protagonists that do not end up with their love interests (Colleen and Elisa, respectively).
- Also, as he is from Dublin, Ireland, Dinty is one of the only Rankin/Bass characters, besides those who live in the North Pole, who have been revealed to live in a real-life place.