In "The Oracle of the Dog" by G. K. Chesterton, the daughter of a murdered rich colonel was talking about her husband, a nobleman and skilled surgeon, who wanted to challenge the secretary to a duel, for he was angry with him, because the secretary accused him of murdering the old colonel. She said:
“Does [the secretary] think my husband, who has given up a crest and a coronet as old as the Crusades for his principles, would kill an old man in a summer-house for a legacy like that?” Then she laughed again and said, “My husband isn’t killing anybody except in the way of business. Why, he didn’t even ask his friends to call on the secretary.”
What's the meaning of business here?
Knowing that he wanted to kill the secretary in the duel, but his wife dissuaded him?!