As Halloween draws close, Scrooge, Cratchit, and their newly married junior partner Sherlock "Lockie" Holmes, father of the great detective, are pulled into the complex murders of three Irishmen: a nobleman, a town mayor, and a pubkeeper. To Scrooge's utter dismay, the three sail to Ireland, where they uncover biblical secrets and face a wide range of challenges and assailants.The trio is aided by two sharp female protagonists: one is an accomplished scientist, the other is developing martial arts skills. A crafty lawyer intends to seize the mines belonging to Lucy Holmes and her cousins, Abigail and Samuel Jiggins. An ancient cult is forming, and a young mastermind continues to plot in the shadows.

Set during the horrendous Irish Potato Famine, Treasure and Murder in Ireland follows the trio as they struggle their way through dangerous circumstances, gathering clues and discovering magic does not always belong in myths.