From the first page of the book:
"This investigative adventure comes complete with abridged rules and pregenerated characters and contains almost everything you need to play Maelstrom Domesday. The adventure should take roughly 1-3 game sessions to play through and can be run with as many characters as desired.
The miller in the village of Welburn has stopped grinding grain into flour, and Count Robert of Mortain will not be happy when he finds out. A motley band of investigators are sent to investigate the strange goings on in the new mill.
Will they succeed? What is the secret?
This adventure does not require the core Maesltrom Domesday rulebook to play, although the adventure can easily be played with the full version of the rules."