"I can tell you this," he said. "If Vervick had written, in letters, his own name upon these pieces metal, it would not have been more plain to me.
"I can tell you also this. By these pieces of metal, I see that the bomb was made in America, here. But I had thought that Vervick was not here!"
"But how do you know that he is dead?"
"Because he was the fool! It is for others that he has always done work. These bombs have been made by him, as others have told him to do.
"He was a man who hid. He did not put the bombs where they would explode. He was a fool, that wished for money — and would believe all that was told to him!
"Do you bring to your mind that explosion in the office of the newspaper — the Classic, it was called?"
Cardona nodded.
"Who was the man killed there? The man they did not know? I can tell you that man and his name! It was Isidor Vervick!
"He had made the bombs. He had given them to those who paid for them. He saw five thousand dollars. He went to warn — and before he could warn, he was killed!"
"But who planted the bombs?" questioned Cardona.
"You have not yet found that out? Well, now I shall tell you where to look!
"In New York there must be two men — one is Italian, Michael Sforza. The other — he is Russian, Grigori Pecherkin. Only for them would Vervick have done this work.
"They have been here in New York. What names they have now to call themselves by, I do not know. But they have done nothing here except to talk of communism. But now, I can tell you plain, they have to work with Vervick!"
Before Cardona could speak, the secret-service man grunted his accord with Zerndorff's remarks. This man was no stranger to either Burke or Cardona. He was Hal Steelman, who had cooperated with the New York police on previous occasions.
"I can trace both of those men," he said. "Sforza is working in a Brooklyn restaurant, under his own name. Pecherkin calls himself Peterson. He hangs around on the East Side.
"We've had nothing on either of them, until now. But we ought to get some good evidence before we grab them!"
An attendant entered the laboratory and spoke to Doctor Zerndorff in German. The criminologist turned to Inspector Burke.
"There is a call for you from headquarters," he said. "You wish the telephone, yes? It is waiting with the call."
Burke left, with Cardona at his heels. He returned a few minutes later, alone. His face bore a smile of grim satisfaction.
"They've rounded up some suspects," he said. "Cardona's gone on duty. We'll hear from him at headquarters."
He jotted down the information which Doctor Zerndorff had given him. He compared notes with Steelman. Then he departed for headquarters and the secret-service man went with him.
It was late in the evening when they left. It was not until the next morning that Doctor Zerndorff heard from them. Then he had a visitor in the person of Detective Joe Cardona. The Italian-American grinned when Zerndorff entered the room where he was waiting.
"Well?" asked Doctor Zerndorff.
"Have you seen the newspapers?" questioned Cardona.
"Not as yet," replied Doctor Zerndorff methodically. "I have just breakfasted and I do not read until after then — never."
Cardona pulled a copy of the morning newspaper from his pocket and spread it before Doctor Zerndorff.
Great headlines told of the roundup of the bombers. Police, aided by government agents, had delved to the depths of the mysterious explosions.
"Tell me about it," said Zerndorff quietly. "I should rather hear than read of it."
"Well, you had the right dope, professor," said Cardona. "But we got a great break last night. You remember, I had a clue on the bombing at Grand Central Station? Big packages had been delivered there.
"Well, the bomb went in; it was in a box, and we found out who delivered it. An Italian named Bonzetti, on the East Side. He was working on the truck that delivered cigars.
"He would have got away with it, but there was a mix-up on a couple of big packages. The one intended for the Grand Central cigar store came back to the factory. He didn't know it.
"One of my men pinched him on suspicion yesterday evening. We gave him the third degree last night. He told us plenty."
"Just how much did he tell you?"
"Well, he admitted taking in the package, and after that it was easier. We made him spill some information we wanted and we landed two others of his kind — an Italian named Arno, and a Russian who calls himself Nick Michaels. His right name is Maklakov."
"Ah!" exclaimed Zerndorff. "He is linked with Pecherkin, yes?"
"Exactly! We grilled him and he came through with that information.
"We've got evidence now! More than that, we've pinched Sforza and Pecherkin — or Peterson, as he insists on calling himself."
"Have they talked?"
"Not yet."
"They would have — if they were in Italy or in Russia. It is too easy here." Doctor Zerndorff's face took on a sudden sternness. "But it will not be difficult! How is the evidence which you have found?"
"Well, we've got it on Bonzetti, right enough. He appears to have framed the whole thing. But he only planted one bomb.
"We figure that Arno placed the one in Wall Street. He looked a lot like a fellow who was seen down there early yesterday morning. He's shifty when he talks, but we're getting it out of him.
"We've also got him tied up with the bomb at Columbus Circle, and the one in the office in the Financial Building. He must have had keys to the office of Barr Childs. Where he got them, we don't know.
"But here's the Nick Michaels angle. He was seen around the Classic yesterday afternoon. We've been getting a real line on him.
"How do you think that bomb went up to Raynor's office?"
"How?"
"In a package of newspapers!
"Raynor had two hundred of each edition brought up to him each day when big stories were breaking. We figure that Michaels planted a phony stack of newspapers, with the bomb in them. Then he ditched the regular stack. They were so busy around there that they thought he was just one of the workmen, didn't pay any attention to him.
"You see, the fellow that took up the stack to Raynor's office remembers this guy Michaels watching him. We pinched Michaels last of all. We had a hunch that he had planted the Classic bomb, because we had been accounting for the others.
"We rounded up the heads of different departments at the Classic and got the right guy to identify Michaels."
"That is very good!" declared Doctor Zerndorff. "But tell me this. Have you found any word that brings in these two men who are the ones behind it. These men — Sforza and Pecherkin?"
"No, we haven't," returned Cardona uneasily. "That's the big trouble. We've linked Michaels with them. Very strongly. We're getting evidence to tie up Bonzetti and Arno.
"But we can't get an admission from any of the three that Sforza and Pecherkin had anything to do with it!"
"How do those three defend themselves? You say they have admitted what they have done, yes?"
"Yes and no. Bonzetti says he delivered cigars. He admits he took in the wrong package. He said he was told to do so.
"Arno admits being around Wall Street, Columbus Circle, and the Financial Building, but he doesn't remember anything he did there.
"Michaels admits he was at the Classic office. Says he was looking for a job. He asked for one — that's certain."
"Did you ask them who sent them there?"
"Yes. That's the strange part about it, professor. They say that someone ordered them — but they do not know who it was!
"They declare that neither Sforza nor Pecherkin gave them orders. Bonzetti — he's weakened most because we've had him longest — he let something slip, the word maestro, which means master.
"We've quizzed all of them along that line, and it looks like we may get somewhere with it. Either one of two things is certain — they are pulling a wonderful stall to save Sforza and Pecherkin, or else there is some mystery man mixed up in it — someone they don't know, but someone whom they obey!"