Read it through once

“It is nothing very formidable,” he said, taking a long cigar-shaped roll from his pocket. “It is an ordinary plumber’s smoke-rocket, fitted with a cap at either end to make it self-lighting. Your task is confined to that. When you raise your cry of fire, it will be taken up by quite a number of people. You may then walk to the end of the street, and I will rejoin you in ten minutes. I hope that I have made myself clear?”