Adventures requiring player investigation

[Rockrattled]

What adventures out there require investigation on the player's part? One's I've enjoyed so far have been the Witchfire Trilogy and Freeport Series. These all seem to have had acts or chapters to them. Are there any other modules out there like these that require the players to uncover a mystery not necessarily march through an endless amount of numbered encounters?

 

[Wraith Form]

You didn't specify the level so I'm going from what I know, having just started a group.

First level, which can be scaled up pretty easily:

Dungeon #83, Deep Freeze (technically D&D3 v3.0). Dungeon #88, Thirds of Purloined Vellum (again, v3.0). Dungeon #114, Mad God's Key. Dungeon #123, Salvage Operation (sorta, YMMV). Dungeon #124, Whispering Cairn - the later chapters (again with the YMMV). Dungeon #130, Within the Circle. Dungeon #135, Funeral Procession.

Goodman Games' Dungeon Interludes (Dungeon Crawl Classics #14) and Legend of the Ripper (Dungeon Crawl Classics #21). And GG's The Adventure Begins has a handful of low-level mini-adventures, aimed at 1st - 2nd level. Strong YMMV warning, as most are essentially dungeons, but a few have stronger role-playing and investigative elements, provided you're willing to do some work.