I saw A Dark Song yesterday.
I did not truly understand what Mark was trying to achieve.
Was he honestly accommodating or was his intent to malign?
I think that Mark was aware of the seriousness of the situation and genuinely believed in what they were doing but he was not necessarily caring or trying to help. He was there for a selfish reason; he wanted to ask a favor for himself when the moment would arrive ('invisibility'- to live away from the world).