He thought of wire entanglements; but he could not erect them without his father's knowledge. He thought of a booby-trap; but that was bound to make a noise. He had almost reached home before a plan occurred to him; it pleased him so much that he laughed. There was a large quantity of ammonia solution in the house, kept for household purposes and for use with the refrigerator which was a domestic necessity in this tropical climate. Tim had only recently left school in England, so that his knowledge of chemistry had not yet evaporated. If he heated some of this liquid, and led the vapour into the patio at the critical moment, the fumes would be obnoxious enough, he thought, to choke off any rash intruders.
As soon as he got home, he took into consultation an old mestizo named Andrea, who was gardener and odd man, a family servant of many years' standing. Andrea was rather troubled, and advised that the warning should be given to Mr. O'Hagan; but few could resist Tim's persuasiveness, and the old man at length consented to assist his young master.
Tim's bedroom was next to the office. At the bottom of the wall next to the patio there was a grating which could be removed. That night, when all the rest had retired, Andrea brought to Tim's room a large oil-can with a narrow neck, containing a quantity of the ammonia solution. Tim had already provided himself with a short length of garden hose, with a nozzle at the end. Drawing the rubber tubing over the neck of the can, he placed the nozzle end in the hole from which the grating had been removed, in such a way that when the cock was turned it would allow the fumes to enter the patio within a few inches of the office door. Having lighted a large spirit-lamp beneath the oil-can, he set a chair against the door, on which he could mount to reach a ventilator above, opening on to the patio, and sat down on his bed, quivering with excitement, to wait for the expected attack.
Hours passed, and he grew fidgety. Every now and then he got on the chair, and peeped through the ventilator. All was dark and silent.
"I don't believe they're coming," he whispered disconsolately to Andrea.
"So much the better, señorito," said the old man.
But Tim did not agree with that; he did not want to be disappointed of his fun.
At last he heard a slight sound from without. Jumping on the chair, he peered through the ventilator. He could see nothing, but he guessed by the sounds that the putty was being scraped from one of the glass panes of the French door. Presently he dimly saw several dark, shadowy forms pass from side to side. The men were removing the pane. One after another the intruders stepped quietly across the patio towards the office door. Just as they reached it Tim slipped off the chair, stooped to the floor, and noiselessly turned on the cock of the nozzle.
For a few seconds there was no effect. He heard the slight click of a key as it was inserted in the lock of the office door. But then, as the ammonia fumes began to diffuse, there was a sniff, a stifled cough, and a whispered exclamation. Presently there were louder coughs, long-drawn gasps, and the men, in the effort to repress these fatal sounds, choked and spluttered violently, until, half-blinded, half-suffocated, they turned away, cursing with what breath was left to them, and tumbled over one another in a rush for the door.
At the same moment the door of Mr. O'Hagan's room was flung violently open, and that gentleman, roused by the noise, rushed into the patio in his pyjamas, a gun in his hand. Seeing that the pane was removed, he ran to the door, and sent a charge of duck-shot after the dark figures scampering over the garden-beds. The sound of firing roused all the household, and the affrighted servants came flocking into the patio.