From GameWatcher: "THQ Nordic and Pieces Interactive have announced the standalone prologue for the upcoming Alone in the Dark reimagining is now available to download for free on Xbox Series, PS5, and PC.
Alone in the Dark: Grace features young Derceto resident Grace Saunders in a short combat-less standalone prologue. It acts as a mood and context setter, so will feature no spoilers for the main game if that concerns you."
Exactly where you'd expect. Steam and the PS and Xbox stores.