"A thorough search was made of his house by Count von W——, at the head of twelve men. The result of this search was purely negative, but the grand-duke was nevertheless proved to be in possession of the papers.
"Where had he hidden them? This was a problem which probably nobody in the world would be able to solve at the present moment.
"I must ask for twenty-four hours in which to solve it.
"Arsène Lupin."
And, twenty-four hours later, the promised note appeared:
"The famous letters are hidden in the feudal castle of Veldenz, the capital of the Grand-duchy of Zweibrucken. The castle was partly destroyed in the course of the nineteenth century.
"Where exactly are they hidden? And what are the letters precisely? These are the two problems which I am now engaged in unravelling; and I shall publish the solution in four days' time.
"Arsène Lupin."
On the day stated, men scrambled to obtain copies of the Grand Journal. To the general disappointment, the promised information was not given. The same silence followed on the next day and the day after.
What had happened?