From the Front Cover:
Fort Dalton along the River Lis was long ago destroyed. Now rumors tell of foul cults practicing their dark rites within the fort's ruins. Are the rumors of elemental cults true or are the rumors a cover for some other sinister plot? A two-hour adventure for 1st-4th level characters.
From the Introduction:
Welcome to Dark Rites at Fort Dalton, a D&D Expeditions adventure, part of the official D&D Adventurers League organized play system and the Elemental Evil storyline season.
This adventure is designed for three to seven 1st-4th level characters, and is optimized for five 3rd-level characters. Characters outside this level range cannot participate in this adventure. A player with an ineligible character can create a new 1st-level character or use a pregenerated character.
The adventure is set in the Moonsea region of the Forgotten Realms, in and around the city of Mulmaster and the Flooded Forest to the south of the city.