Sentence:  To die like a man of honour, Sir Hargrave, you must have lived like one. You should be sure of your cause. But these pistols are too ready a <WSD>mischief</WSD>. Were I to meet you in your own way, Sir Hargrave, I should not expect, that a man so enraged would fire his over my head, as I should be willing to do mine over his. Life I would not put upon the perhaps involuntary twitch of a finger. 
Meaning of the word marked with <WSD> tags:  A cause or agent of annoyance, harm or injury, "especially" a person who causes mischief.