The plot has Celtic hero Cuchulainn on a search to find his companion Lóeg in the mysterious city of Dun Darach.

The background history is based on Celtic folklore about the demigod Cuchulainn and his battles against the people of Connachta in ancient Ireland.

He later discovers that Skar is a sorceress and ally of the Connachta, and has taken Lóeg to the Secret City of Dun Darach in retribution for the death of Prince Amhair, who perished in the battle.

Commands the player inputs can have him buy, steal and sell from shops in the city, bet at a casino (Iomain Ludum), and deposit money at a bank with daily compound interest.

[8] Follis claimed that the biggest complaint for Tir Na Nog was its huge setting, resulting in it being scaled back to one city.

There is an empty area in the centre of the city, the pleasure quarter "Iomain" which was originally intended to be a brothel called "Lady Q's" and would have opened into a whole red-light district.

[15] Richard Price for Sinclair User, while describing the game as "less abstract" as Tir Na Nog, said it was more interesting and eventful than its predecessor.

[16] Ian Marks from Retro Gamer compared it to Tir Na Nog, saying both were fun to play but Dun Darach was not as good.