The adventurers start off in Neverwinter, having volunteered to embark on a voyage to Gundarlun. It is up to the players to determine why their character has joined the voyage. The expedition has been commissioned by Lord Dagult Neverember in response to the news of a bizarre crash-landed vessel from King Olgrave Redaxe. The characters travel to Gundarlun but are attacked by sahuagin raiders on the way. After arriving at the crash site on Gundarlun, they have the chance to investigate, and discover that the sahuagin are closely linked to the crash.
Characters who follow up on this uncover that the sahuagin are working in conjunction with a pirate fleet, named the Black Armada, which has planned simultaneous attacks on major cities of the Sword Coast; Neverwinter, Waterdeep, and Baldur's Gate. Each captain has their own reason for attacking, which characters may discover.