Jeremiah Crowell

But Willie isn't in Minnesota. He's halfway across the country at a different crop dusting business. He'd been flying crop dusting planes for decades. On any given day during his regular job, he'd pack as much as 500 gallons of pesticides into his Air Tractor 502 crop plane. He'd fly incredibly low to the ground to avoid spraying homes and people.

But Willie isn't in Minnesota. He's halfway across the country at a different crop dusting business. He'd been flying crop dusting planes for decades. On any given day during his regular job, he'd pack as much as 500 gallons of pesticides into his Air Tractor 502 crop plane. He'd fly incredibly low to the ground to avoid spraying homes and people.

But these men didn't sound like they wanted that experience. They were asking about tank capacity and flight distances. It sounded off. So six weeks before September 11th, Willie called the police. But the police didn't do anything about it. They couldn't really. No one had done anything illegal.

But these men didn't sound like they wanted that experience. They were asking about tank capacity and flight distances. It sounded off. So six weeks before September 11th, Willie called the police. But the police didn't do anything about it. They couldn't really. No one had done anything illegal.

After 9-11, when Willie saw the names and pictures of the hijackers on television, he knew he'd been right to be suspicious. Because some of the men who'd visited him were the same men who flew the planes into the Twin Towers. In fact, one of them was Mohammed Atta, the chief U.S. operative who directed the attack. Willie and his team called the FBI. This time, they took action.

After 9-11, when Willie saw the names and pictures of the hijackers on television, he knew he'd been right to be suspicious. Because some of the men who'd visited him were the same men who flew the planes into the Twin Towers. In fact, one of them was Mohammed Atta, the chief U.S. operative who directed the attack. Willie and his team called the FBI. This time, they took action.

So now the FBI has a question to answer. Why were Al-Qaeda members in at least two different places around the country trying to learn how to fly crop dusters? And meanwhile, there's another team with a question the FBI hasn't heard about yet. Dr. Bush and his colleagues, who are trying to figure out how a man in suburban Florida has anthrax. And now those two mysteries are about to collide.

So now the FBI has a question to answer. Why were Al-Qaeda members in at least two different places around the country trying to learn how to fly crop dusters? And meanwhile, there's another team with a question the FBI hasn't heard about yet. Dr. Bush and his colleagues, who are trying to figure out how a man in suburban Florida has anthrax. And now those two mysteries are about to collide.

Because the airfield that the 9-11 terrorists visited, Willie's airfield, it's less than an hour away from the home of anthrax patient Robert Stevens. Back in that hospital, Robert Stevens' health is deteriorating. And Dr. Bush still doesn't know for certain what he's dealing with.

Because the airfield that the 9-11 terrorists visited, Willie's airfield, it's less than an hour away from the home of anthrax patient Robert Stevens. Back in that hospital, Robert Stevens' health is deteriorating. And Dr. Bush still doesn't know for certain what he's dealing with.

He hung up. The people he works for are high up on the chain. In an instant, the CDC calls the National Department of Health, who calls the White House, who calls the Department of Justice. And now, finally, the FBI learns anthrax is in Florida. Because of his background in science, Agent Scott Decker knows an anthrax infection shouldn't have happened in Florida.

He hung up. The people he works for are high up on the chain. In an instant, the CDC calls the National Department of Health, who calls the White House, who calls the Department of Justice. And now, finally, the FBI learns anthrax is in Florida. Because of his background in science, Agent Scott Decker knows an anthrax infection shouldn't have happened in Florida.

So for the FBI, who'd been worried for weeks about some kind of biological attack, likely from the air, maybe involving crop dusters, if this isn't the work of the same 9-11 terrorists, who they now know took flight lessons at an airfield only an hour away, it's an awful lot of coincidences.

So for the FBI, who'd been worried for weeks about some kind of biological attack, likely from the air, maybe involving crop dusters, if this isn't the work of the same 9-11 terrorists, who they now know took flight lessons at an airfield only an hour away, it's an awful lot of coincidences.

And in order to do this, prove its terrorism, Decker and the FBI need to know what kind of anthrax this is. Because anthrax comes in strains, like the flu. And if they can figure out the strain, that might tell agents where or how Stevens got infected.

And in order to do this, prove its terrorism, Decker and the FBI need to know what kind of anthrax this is. Because anthrax comes in strains, like the flu. And if they can figure out the strain, that might tell agents where or how Stevens got infected.

FBI agents head to the state park to look for any signs that Stevens could have been infected in nature. But the scarier scenario is that the anthrax came from a laboratory. Because if it's from a lab, there's a good chance somebody spread it on purpose. To figure this out, the FBI knows exactly who to turn to.

FBI agents head to the state park to look for any signs that Stevens could have been infected in nature. But the scarier scenario is that the anthrax came from a laboratory. Because if it's from a lab, there's a good chance somebody spread it on purpose. To figure this out, the FBI knows exactly who to turn to.

Dr. Paul Keim hoped to find the source of the anthrax in a biological database he'd been creating for decades.

Dr. Paul Keim hoped to find the source of the anthrax in a biological database he'd been creating for decades.