What starts out as a simple and predictable treasure hunt plot quickly transforms into a much more complicated story, with a surprisingly large cast of characters and convoluted backstory. This only becomes more engaging as the expansion goes on, and unlike the original game's story, Pirates rarely meanders, instead using its new quests to add more and more layers. The pirate theme and the central characters actually end up dwarfed by larger things very quickly, and I was impressed to find that it was more than just a gimmick in the end.
Where Pirates also shines is in its choice & consequence. While not as extensive as other games, there are a few big choices to be made during the story that can lead to fairly different story outcomes, and certain quests will be made available or cut off based on the things you do and say. There are even a few opportunities to lie, misdirect or backstab different characters; in the hands of some developers these could have come off as simple good/evil choices, but Pirates has quite its share of morally ambiguous situations and characters to make these decisions interesting.