I do not know why at the moment I could think of no excuse. I followed them rather sulkily to the table at which Strickland always sat, and he called for the board and the chessmen. They both took the situation so much as a matter of course that I felt it absurd to do otherwise. Mrs. Stroeve watched the game with inscrutable face. She was silent, but she had always been silent. I looked at her mouth for an expression that could give me a clue to what she felt; I watched her eyes for some tell-tale flash, some hint of dismay or bitterness; I scanned her brow for any passing line that might indicate a settling emotion. Her face was a mask that told nothing. Her hands lay on her lap motionless, one in the other loosely clasped. I knew from what I had heard that she was a woman of violent passions; and that injurious blow that she had given Dirk, the man who had loved her so devotedly, betrayed a sudden temper and a horrid cruelty. She had abandoned the safe shelter of her husband's protection and the comfortable ease of a well-provided establishment for what she could not but see was an extreme hazard. It showed an eagerness for adventure, a readiness for the hand-to-mouth, which the care she took of her home and her love of good housewifery made not a little remarkable. She must be a woman of complicated character, and there was something dramatic in the contrast of that with her demure appearance.

请教老师：

for what she could not but see was an extreme hazard. 中怎么理解could not but see 这一结构含义和用法？

另外，with her demure appearance. 这里的with怎么理解？

还有，标注黑体的句子( I scanned her brow for any passing line that might indicate a settling emotion.)的意思看不懂？

谢谢老师！