"What were you doing there?"

"I was at work there. When I heard Mr. Hart, or the man, whatever his name is, coming down stairs, I went up and met him in the entry. You can go down cellar, if you like."

"I think we will," said Mr. Checkynshaw.

The detective looked into the bed, under it, in the closets, drawers, and into the seaman's chest which contained Leo's wardrobe. He did not expect to find anything, and his search was not very thorough. He examined the till, and felt in the clothing; but he did not put his hand down deep enough to find the papers the robber had deposited there. If the rogue had left anything, he had no object in concealing it; and Mr. Clapp reasoned that he would be more likely to leave it in sight than to hide it.

When the search had been finished in the room, and the result was as the detective anticipated, Leo led the way to the cellar. Here was presented to the visitors a complete revelation of the boy's character and tastes—a revelation which assured the skilful detective, deeply versed as he was in a knowledge of human nature, that Leo was not a boy to be in league with bad men, or knowingly to assist a robber in disposing of his ill-gotten booty.

The cellar or basement was only partly under ground, and there was room enough for two pretty large windows at each end, the front and rear of the house, and in the daytime the apartment was as light and cheerful as the rooms up stairs. Across the end, under the front windows, was a workbench, with a variety of carpenter's tools, few in number, and of the most useful kind. On the bench was an unfinished piece of work, whose intended use would have puzzled a philosopher, if several similar specimens of mechanism, completed and practically applied, had not appeared in the cellar to explain the problem.

On the wall of the basement, and on a post in the centre of it, supported by brackets, were half a dozen queer little structures, something like miniature houses, all of them occupied by, and some of them swarming with, white mice. In the construction of these houses, or, as André facetiously called them, "Les Palais des Mice," Leo displayed a great deal of skill and ingenuity. He was a natural-born carpenter, with inventive powers of a high order. He not only made them neatly and nicely, but he designed them, making regular working plans for their construction.

The largest of them was about three feet long. At each end of a board of this length, and fifteen inches in width, was a box or house, seven inches deep, to contain the retiring rooms and nests of the occupants of the establishment. Each of these houses was three stories high, and each story contained four apartments, or twenty-four in the whole palace. The space between the two houses was open in front, leaving an area of twenty-two by fifteen inches for a playground, or grand parade, for the mice. The three sides of this middle space were filled with shelves or galleries, from which opened the doors leading into the private apartments. The galleries were reached by inclined planes, cut like steps.

Monsieur Souris Blanc passed from the gallery into one room, and from this apartment to another, which had no exterior door, thus securing greater privacy, though on the outside was a slide by which the curious proprietor of the palace could investigate the affairs of the family. Madame Souris Blanche, who considerately added from four to a dozen little ones to the population of the colony every three or four weeks, apparently approved this arrangement of rooms, though it was observed that three or four mothers, notwithstanding the multiplicity of strictly private apartments, would bring up their families in the same nest, cuddled up in the same mass of cotton wool.

Over the "grand parade" was a roof, which prevented the mice from getting out over the tops of the nest-houses. Though this space was open in front, and the play-ground protected only by a fence an inch high, the little creatures seldom fell out, for it was five feet to the floor of the cellar, and this was a giddy height for them to look down.