Question of Sevens

It was understood; no one went out on the night of the new moon. From dusk to dawn, no matter the season, everyone and everything was indoors, behind shutters bound with iron and bay.

 An easy thing, to leave a shutter ajar. To slip out into the star-gilded night… and find, on returning, blood spattered ruin where once had been a cozy farmhouse. What could possibly have happened?