By the duel itself the accused had offended against the recent enactment, and, moreover, the irregular manner in which the encounter had been conducted, without seconds or witnesses, rendered the accused answerable to a charge of murder, if it could be proved that he actually did engage and kill the deceased.

Major Swan thought this could be proved.
The irregularity of the meeting must be assigned to the enactment against which it offended.

A matter which, under other circumstances, considering the good character borne by Captain Tremayne, would have been quite incomprehensible, was, he thought, under existing circumstances, perfectly clear.

Because Captain Tremayne could not have found any friend to act for him, he was forced to forgo witnesses to the encounter, and because of the consequences to himself of the encounter's becoming known, he was forced to contrive that it should be held in secret.

They knew, from the evidence of Colonel Grant and Major Carruthers, that the meeting was desired by Count Samoval, and they were therefore entitled to assume that, recognising the conditions arising out of the recent enactment, the deceased had consented that the meeting should take place in this irregular fashion, since otherwise it could not have been held at all, and he would have been compelled to forgo the satisfaction he desired.
He passed to the consideration of the locality chosen, and there he confessed that he was confronted with a mystery.