From the Front Cover:
Decades have passed since Sokol Keep was reclaimed, and a small garrison placed there along with a beacon to help guide ships. Now, that beacon has gone dark, and the garrison has disappeared. In Phlan, rumors circulate that something ancient was discovered in the grounds beneath the keep, dating to before the clerics of Tyr built the small fortress. Uncover the secrets of Sokol Keep! An adventure for 1st-4th level characters.
From the Introduction:
Welcome to Secrets of Sokol Keep, a D&D Expeditions adventure, part of the official D&D Adventurers League organized play system and the Tyranny of Dragons storyline season.
This adventure is designed for three to seven 1st-level characters, and is optimized for five 2nd-level characters. Characters outside this level range cannot participate in this adventure. Players with ineligible characters can create a new 1st-level character or use a pregenerated character.
The adventure starts in the city of Phlan in the Laughing Goblin at the docks, but quickly takes the characters to Sokol Keep on Thorn Island near the harbor of Phlan.