Although Uncle Brian was perfectly aware that the Rioguayan authorities could inspect the building at any time, his careless assurances, coupled with the warning that any interference might destroy the fruit of months of research, had resulted in a state of immunity. He was allowed to carry on undisturbed. But on the other hand, he guarded himself against a possible visit from his State employers. There were drawings in the office, but they referred to commonplace machinery and appliances. Of his invention, his _magnum opus_, no plans were in existence, save those that lived in his brain. He took extreme caution lest the future enemies of his country should score on that point. Producing a bunch of keys, Uncle Brian unlocked the comparatively frail door and switched on a light. Peter was about to cross the threshold when his uncle stopped him. "Half a minute," exclaimed Uncle Brian. "Wait till I've put little Timothy to bed." His nephew looked in astonishment. Right in the middle of the concrete floor was a coiled-up snake. Hearing footsteps, the reptile raised its head, revealing a pair of deep-set eyes that glittered in the artificial light. Without hesitation, Uncle Brian grasped the snake at a point about four inches behind the head. The reptile immediately coiled itself round his arm. "Timothy is quite harmless," explained Uncle Brian. "I got him from an old Indian up-country. I need hardly say the poison sac has been removed. He makes an excellent guard." "So I should imagine," remarked Peter. "Dashed if I could handle the brute, poisonous or otherwise." The snake was placed in a box. Uncle Brian poured out some milk from a bottle, placed the saucer beside the reptile, and closed the lid. "Now we can get to work," he said briskly. Peter glanced around him. There was little or nothing to suggest anything mysterious about the place. On one side of the building was a long bench, absolutely littered with tools, scraps of metal, old bottles, and other debris, together with a lathe and an engineer's vice. Underneath the bench was a similar assortment of rubbish. "Bit of a lash up, eh?" commented Uncle Brian. "'Fraid I am a bit untidy, but I can generally clear a space when I want to get to work. Bear a hand and shift some of this stuff." He pointed to a confused heap at one end of the bench. When the pile of stuff was removed there stood revealed a small contraption that looked as if it were a box camera with an acetylene motor-lamp attached. "There's my patent searchlight," he announced, with boyish enthusiasm. "Don Ramon Diaz and all his precious pals can fool about with that to their hearts' content. They won't be a penny the wiser. Look at it. See if you can make anything of it." Peter did as he was requested. "Can't make head or tail of it, Uncle," he confessed frankly. Uncle Brian proceeded to connect up a couple of terminals with a wall switch.