Beautiful Dog took another step toward the chair.  And then there paced into the library, and caught him in the rear, his arch enemy—­Sir Thomas More Black.  The great cat took one look at the nigger dog trespassing upon forbidden ground.  You could see Sir Thomas More swell with rage and astonishment, and then lengthen out like an accordion.  Without a sound he launched himself upon the intruder.  And at the same instant and actuated by the same motive, Potty Black, who had been sweetly and peacefully dozing on my lap, rose up with slitted eyes, bottle-brushed her tail, and hurled herself into the fray.

Attacked front and rear, Beautiful Dog was at hideous disadvantage.  He launched himself sidewise; he didn’t even have time to howl.  He fell over his own splay feet as he ran, butted into chairs and tables, twisted, turned, whirled, dodged, but always presented just the right spot to be clawed.  He couldn’t dash to the door and escape:  the cats were too swift for him.  They kept their bewildered victim circling around the middle of the room.

I was sorry for Beautiful Dog, for my sleek, petted, purring pussies had turned into raging black tornadoes edged with a lightning of claws.  If the aristocratic Black Family had been raised in Hooligan’s Alley itself, on the soft side of the ash-bins, they couldn’t have behaved more villainously.  Alas! they were cats, just as people are people.

I snatched up the brass-headed poker, the readiest thing to my hand.  I merely wished to shoo off the Blacks with it.  But as I rose from my chair with a scat! upon my lips, Beautiful Dog, seeing out of the tail of his eye a chance to escape, dashed headlong into me.  He came with such force that I fell backward, and the poker flew out of my hand and came crack! upon the sacred tiles of Hynds House library.  There was an ominous clatter, for no less than the Father of his Country himself had fallen out of his place.  At the same instant Beautiful Dog gained the door, with both cats upon his hind quarters; with one prolonged yell of terror he made for safety and Mary Magdalen.

I picked myself and the tile up.  Thank Heaven, it wasn’t broken.  The blow had loosened the cement that held it in place, and where it had been was a small square hole.

I looked at that hole doubtfully.  There oughtn’t to be any hole there at all.  That was a curious way to fix tiles, such precious tiles as ours.  I slipped my hand in and tentatively tested the black wall, and discovered that the other tiles, as might be expected, had been properly put in; that is, against a solid background.

I put my hand farther into the aperture.  It was larger than might be expected, and most cunningly contrived—­a hollow space some ten inches in width, and possibly a foot deep.  There was something in it.