My stragy is not the best one but i killed Samuel.
First i opened the door of Samuel's room but i did not stay too long in the room.
I run quickly and i went back in the first room of the level.
A few shadows followed me and i killed them.
I killed the shadows in the second room and in the third room and i saved the game.
Then i could fight Samuel alone. I had to use a lot of potions for killing him.
It was not an easy fight.

What is the kind of your characters ?

Barta