I found Dirk waiting for me on the steps. He seemed to see nothing, and did not notice that I had joined him till I touched him on the arm. We walked along in silence. I tried to imagine what had happened to drive the poor creature to that dreadful step. I presumed that Strickland knew what had happened, for someone must have been to see him from the police, and he must have made his statement. I did not know where he was. I supposed he had gone back to the shabby attic which served him as a studio. It was curious that she should not wish to see him. Perhaps she refused to have him sent for because she knew he would refuse to come. I wondered what an abyss of cruelty she must have looked into that in horror she refused to live.

上面黑体字中， for someone must have been to see him from the police: must have been to - 这里表示推测，原来是be to结构吧？用在这种must have been to结构中，表示什么意思呢？

另外，结尾处，黑体字中that in horror中的that是引导定语从句she refused to live作宾语吧？