All at once they heard some one call out, and raising their heads, perceived in the frame of the bars of the window something of a white color, like a hand that was waved backwards and forwards — something shining, like a polished weapon struck by the rays of the sun. And before they were able to ascertain what it was, a luminous train, accompanied by a hissing sound in the air, called their attention from the donjon to the ground. A second dull noise was heard from the ditch, and Raoul ran to pick up a silver plate which was rolling along the dry sand. The hand that had thrown this plate made a sign to the two gentlemen, and then disappeared. Athos and Raoul, approaching each other, commenced an attentive examination of the dusty plate, and they discovered, in characters traced upon the bottom of it with the point of a knife, this inscription: