The Door With Seven Locks by Edgar Wallace

At ten o'clock the next morning Dick Martin walked blithely into Lincoln's Inn Fields. The birds were twittering in the high trees, the square lay bathed in pale April sunshine, and as for Slick, he was at peace with the world, though he had travelled nigh on thirty thousand miles and had failed to report at the end of them.

Messrs Havelock and Havelock occupied an old Queen Anne house that stood shoulder to shoulder with other mansions of the period. A succession of brass plates on the door announced this as the registered office of a dozen corporations, for Mr Havelock was a company lawyer, who, though he never appeared in the courts, gave the inestimable benefit of his advice to innumerable and prosperous corporations.