Мафия 15. Cosa Nostra.

Hos heard them, which means this ND was applied to him.

...The next person to complain about the nighttime events was Gabriel (Xostor). He slept poorly at night – he imagined the sound of hooves and horses neighing – as if carriages were driving past his house all night.

At first glance, this looks like an ND applied to Hostor. But, considering the fact that the murder took place under his windows, it could very well be a clue. There is no other text that could indicate a hint, except for the unlikely phrase "unconscious state."
I won't vote yet.