Spoilers included in this review.
Sokol Keep is one of the first adventures for the AL line, and it features some issues that will crop up for many of these modules. While it has a solid story, it lacks a good hook to involve the PCs, and there's no good way for the players to learn the complex backstory and events that are driving the plot.
The lighthouse in a busy harbor being dark for a couple of nights seems like a big problem for a lot of people. The island is only 300 feet from the docks. PCs may ask why nobody has taken the 5 minute boat ride over there to just ask what's wrong. It makes little sense.
The module assumes the characters are so interested in the lighthouse (for no reason), that they will go to the Sokol family's rep and ask her permission to go out to the lighthouse island to investigate/fix it. "Please may we go investigate why your lighthouse is broken? No charge, of course."
My recommendation is to say the Sokol family rep has specifically called together and hired the characters to go investigate the trouble at the keep. She visited herself the previous day and talked with the groundskeeper, to discover that both the young noble and all of the guards are missing, which is of course concerning. She's keeping the trouble quiet for now (the Sokol family doesn't want anyone questioning their ability to take care of the lighthouse), and has told the local government it's a minor problem that will be repaired soon. She wants the characters to go over there and get things straightened out. This gives them a reason to go, and also lends some urgency to getting it fixed quickly.
Secondly, I'd give the spirit on the island a scene where she's able to fully manifest and talk with the characters, giving them the full backstory about the young noble, the corrupt guard captain, etc., at some point near the end.
I'm giving this module 4 stars, because it has its heart in the right place, and the issues above can be changed and worked around, but they really should have been caught before publication.
[4 of 5 Stars!]