At the end of Chandler's The Lady in the Lake, when Kingsley is interrogated by Marlowe he says that he believes that his secretary Adrienne Fromsett knew that the person who called claiming to be his wife was not really his wife:

I looked at Kingsley and said: "You didn't talk to her on the phone, you said. What about Miss Fromsett? Did she think she was talking to your wife?"

Kingsley shook his head. "I doubt it. It would be pretty hard to fool her that way. All she said was that she seemed very changed and subdued. I had no suspicion then. I didn't have any until I got up here. [...]"

This is a serious allegation. In context I don't understand why Fromsett would have done what is alleged and why Marlowe, etc., do not seem to care.

Earlier Marlowe had insinuated that Kingsley and Fromsett were having an affair, but I read that as having been misdirection, akin to acting as though he believed Kingsley's scarf at the crime scene was evidence of murder, intended to concoct a plausible story to lure Degarmo into a situation in which he could be apprehended. Throughout the story Marlowe has seemed to like Adrienne Fromsett, viewing her as elegant and trustworthy.