Set along the Sword Coast of the Forgotten Realms, the adventure begins as three wandering heroes, Vahn, Adrianna, and Kromlech, arrive in the bustling city of Baldur's Gate. Their journey takes a violent turn almost immediately when a band of thieves ambushes them in the streets. Saved by the city watch, the battered trio are brought to the Elfsong Tavern to recover, where the grateful bartender enlists their aid with a seemingly simple task in the cellar below. What starts as clearing out a rat-infested basement quickly unravels into something far more sinister, as the heroes discover the thieves have been slipping into the city through its sewers. Drawn ever deeper beneath Baldur's Gate, the three adventurers set out to uncover the growing threat lurking in the shadows.