From publisher blurb:
It starts with a letter. Then tapping at the window at night. Soon, friends and foe alike are revealing themselves as assassins. Your players will have to find word around town about the sinister Assassin Clan, and then use all of their investigation skills to discover the Clan's hideout. Once there, they will have to fight their way through countless traps, and defeat the leader of the ninja clan once and for all.
The Assassin's Hideaway was originally written and optimized for a party of Level 8 characters, though is primarily narrative-based and may be adapted to all levels.