Private investigator Regan Reilly and her husband Jack, head of the Major Case Squad in New York City, have just gotten hitched! They've headed to Hennessey Castle, a romantic spot in western Ireland, to escape the world and the criminals they deal with daily. But their getaway is anything but relaxing.

Their first afternoon in Ireland, Regan and Jack stop at an old graveyard on the edge of town where they find a tombstone marked Reilly. Intrigued, they discover it belongs to a talented lacemaker by the name of May Reilly, who died in 1822. Legend has it that after making an exquisite tablecloth for a banquet at Hennessey Castle, May was never paid and she has haunted the castle ever since. That same night, the hotel's fire alarm sounds, the guests are temporarily evacuated, and the next morning May Reilly's famous tablecloth is discovered missing. When two international jewel thieves claim responsibility for the theft in a taunting note to Jack who has been on their trail for more than a year, the Reilly's honeymoon comes to an abrupt end.

Working with Regan's Irish cousin Gerard Reilly, Regan and Jack are in for the adventure of a lifetime through the tiny villages and crowded pubs of the Emerald Isle.