Or notSkywalker a écrit :The PCs race back to Meddu and stop Caxtos and his men.
Something common in the Esteren official scenarios, as you will see when the prologue will be delivered to the backers, is that you can't solve all the problems and you will be bound to make a choice sooner or later and you won't like it.
Maybe the white lady can try to explain them that by destroying her, they will unleash the power of the possessed sword, and if the players manage to make the white lady disappear when they return to the village it's already too late to save the mother and the child.
As far as Caxtos is concerned, he doesn't even need mercenaries from another country to defend himself, you can add the fact that tensions already existed in the village regarding the title of Ansailéir (eg. the ansailéir is the second son, his father preferred to give him the title rather than giving it to caxtos but it goes against the traditions, or the ansailéir is firstborn but a woman and people think the title shouldn't be given to a girl), and that the possessed sword only pushed Caxtos to do what he was wishing for some times now.
He could simply find villagers who support him for that coup, but who get concerned because Caxtos seems to turn mad and madder.
That way the player may talk their way out with the guards and avoid direct confrontation. Combat is really really really deadly in the SoE, and players should avoid it unless really necessary.
PS : full moons being very common, such a spirit would have caused the death of hundred of newborns over the years, maybe you could find a less... frequent situation.
Moon eclipse, "blood moon", things like that...
What the PCs do will be open and if they take a risky course of action, I won't be pulling any punches