Black Veil, Covered Up
Noun
くろいきり
ホームステイ先のお父さんが、今日の夕飯の際に黒い霧事件について説明をしてくれました。
My home stay father explained the Black Mist Scandal to me at dinner tonight.
A black fog is going to be a really thick fog or black veil that covers suspicious acts or crimes. It's not a literal cloud of fog or a physical veil, it's what you hide your bad deeds in, metaphorically speaking.
The reading comes from 黒い and 霧.