Then the telephone rang again. Kennedy went to answer it. He came back very excited. "That was the girl--Penny," he said. "She may have something. She described a piece of round glass and said her grandfather had found it in his pocket tonight as he left the museum. She wanted to know if we had found it. I didn't. Did you?" "No," Rocks answered. "But I can't see how it is important." "Nor can I," Kennedy answered. "But it might be. I'll call and see if it has been found. She also mentioned another thing, and this, I think, is really important." "What was it?" "She said her grandfather was writing at his desk when he was killed. The piece of paper on which he was writing was under a blotter and we missed it. She found it. The old man had written a single question on it." Rocks had risen from his chair. Here, he realized, might be a clue that would lead them to the capture of the incredible creature that was loose within the city. "What was the question?" "'Why did Morton weigh the box a second time?'" Kennedy said. "Why did he--" Rocks sat down again. His eyes went across the room to the box. It was sitting on the scales where Morton had placed it. "It's routine here," Rocks said slowly, "to weigh all specimens as soon as they are brought in. Many statuettes, etc., were constructed as hiding places for gems. We weigh them, compute their specific gravity, and thus determine if they contain a hollow place that might be worth investigating." His eyes lit up. "Morton weighed that box before it was opened. He opened it, and something came out of it. But, from Sharp's description, they were in doubt as to whether something had really come out of the box. There was one way to prove something had come out of it--weigh it again and check its present weight with its weight when it was brought in." Rocks leaped across the room to the scales, checked the weight of the box. It weighed 121 pounds. Quickly he found Morton's notes and located the weight of the box when it was first brought to the museum. "Before it was opened it weighed an even 130 pounds," he said. "Now it only weighs 121. That proves that something came out of it." Kennedy whistled. "Nine pounds of sudden death. Well, we don't need any proof to know that something came out of that box. We've got two dead men to prove it. Look," the detective finished, "I'm going back to McCumber's residence and see if I can locate that piece of glass. You keep trying to crack that language." He went out of the room on the run. The motor of the squad car howled to sudden life outside as the detective left. Rocks expected Kennedy to return. But he didn't come back that night. He called instead. "I'm at the undertaker's. They didn't find any piece of red glass. I've been over McCumber's house with a magnifying glass. It isn't there. Either the thing that killed him destroyed it, or somebody picked it up. You getting anywhere with that language?" "No," Rocks groaned.