Whispers In The Dark is a tremendous set of rules for investigative horror using D&D 5e as it's basic game engine.

For anyone looking for a way to game mystery/horror in a late 19th century setting Whispers really shows off the versatility of the D&D rules. Skills, Feats, and Backgrounds are the focus of character creation and the tools that drive players' ability to navigate through their adventures without swords and spells.

In addition to being its own complete game to explore supernatural and the mythos I feel this would also be a great a toolkit for adding options to other 5e based horror game settings like Ravenloft.