One of my favorite modules as a young person was “The Assassin’s Knot,” designated as L2, following “The Secret of Bone Hill” as L1. What made L2 special was that it was a small little sandbox the PC’s could explore, while simultaneously having things unfold in game-time that pressured the adventurers to keep going. The crux of the module is a murder mystery, complete with suspects, ambushes, and surprise revelations.
Inspired by this AD&D adventure from yore, I have placed my gaming group in a mystery of their own, this time tracking down members of a cult of humans that follow Yeenoghu, the god of the gnolls that have been attacking the area. I lifted heavily from the original module, while modifying it both for the plot and for the ruleset.
It will be interesting to see how this goes–I haven’t run a mystery plot since they were second level, so I hope this adventure series goes as well as that does.