Мафия 35. The Heads

But what's the point of acting this way when the Mafia are dead? There's no one else to look for – you need to eliminate the last threat.

I agree that this isn't the most logical option. But it was at least not the only illogical thing in this game. And who, besides Demi herself, can know what motives guided Demi in using the Night Detective in this way that night? We can only speculate. Although, for some reason, it seems to me that there was some logic behind this move.