"Mistook me?" I repeated, catching at the chance for an explanation. It is not pleasant to think of a gentleman and officer turned assassin. "Yes," he answered. "I have made this my privilege. Any man in Chihuahua who wishes to serenade Senorita Vallois has my pledge that I will kill him." "I am in Chihuahua, and I have serenaded Senorita Vallois," I replied. "But you did not know of my pledge. I will spare you this time." "_Muchas gracias_, senor. Yet it seems to me it is a question of my sparing you." "In that case, Senor Robinson might do well to consider that His Excellency, the Governor-General, would gladly welcome an excuse to garrotte a certain _Americano_ spy." "That may be. Still, a sword prick in the back is fair evidence against a dead assassin, even in a prejudiced court." "True. Then it may be that the _Americano caballero_ is sufficiently gallant to consider the scandal of a slaying beneath the window of a senorita of his acquaintance." "A scandal which, it seems, one Lieutenant Medina did not consider. For all that, the argument is sound, _Vaya!_" I ordered, lowering my pistol. "No!" he rejoined. "I will not go and leave you here." "You shall!" "_Nada!_" For a moment I stood quivering with fury, wild to leap in, sword or no sword, and strike him down with my bare fist. But he had spoken truth. A death, or even a loud quarrel, beneath my lady's balcony, would draw upon her the talk of all Chihuahua. "You are right in this," I forced myself to say; "we owe it to the lady not to involve her in any scandal. You will give me your word, and I will give you mine, to start in opposite directions, and neither return here to-night." "Agreed!" he responded. "You have my word to it, senor physician." "And you mine," I said, wheeling. With punctilious precision he wheeled the other way and swaggered up the street as I stalked down. With a last glance at the empty balcony of my lady, I darted off across the corner of the plaza. Almost in front of Walker's quarters I ran plump into the midst of a night patrol. "_Arreste!_" cried the officer in charge, and I stopped short with half a dozen lances at my breast. "_Americano!_" I exclaimed. "_Vaya_," said the officer. The lance points flew up. I darted on through the gateway and around the court to the rooms assigned to Walker. Our host and Pike had retired, but old Caesar was dozing beside the door. I sent him hobbling to bed with a few _medios_ to tickle his black palm, and the moment he had disappeared, drew out my precious missive in the light of the guttering candle.