Four Georgia men arrested this week in connection with a scheme to carry out an attack with explosives and a deadly toxin drew inspiration from an online novel, according to court documents.

But some of their plans, an expert said, may not have ever escaped the realm of fantasy.

From al-Qaeda to neo-Nazis, numerous groups have imagined carrying out a deadly terrorist attack using the highly lethal extract of the castor bean known as ricin. None has succeeded.

Small batches of the virtually odorless toxin, however, have been used effectively as an assassination weapon, and in recent years there have been a handful of U.S. cases in which individuals trying to manufacture it have been arrested.

Even though the alleged Georgia plot appears to have had a fly-by-night character to it, officials indicated that the suspects’ intentions — targeting U.S. government buildings and officials with firearms, explosives and ricin — were deadly serious.

The men contemplated targeting Atlanta and other U.S. cities, including Washington, perhaps by dispersing ricin from interstate highways, the court documents said.

“As in any case, whenever a group of individuals expresses a willingness to commit violence and takes steps to carry out such plans — including attempts to obtain weapons or produce ricin — we have an obligation to take it seriously,” said a senior law enforcement official, speaking on the condition of anonymity because the case is ongoing.

The four men, who ranged in age from 65 to 73, appeared Wednesday in a Georgia courtroom, where they said they needed more time to prepare for a bail hearing, according to local news reports. Relatives of the men have denied the charges.

Ricin is regarded as one of the world’s most toxic natural substances, so poisonous that a dose the size of a few grains of salt can kill and for which there is no antidote. But even governments with dedicated weapons laboratories have struggled to create a ricin weapon that can kill on a large scale.

Experts said that the chances of four men in Georgia successfully pulling off such an attack were not good. “Absolutely zero,” said Raymond Zilinskas, a microbiologist and expert on chemical and biological weapons.

Castor beans are relatively easy to obtain, and recipes for extracting the toxin can be found on the Internet. But Zilinskas, director of the Chemical and Biological Weapons Nonproliferation Program at the James Martin Center for Nonproliferation Studies in Monterey, Calif., said that obtaining the recipes was a far cry from weaponization.

“It is beyond the capabilities of anyone except professional weapons scientists,” he said.

According to court documents, the Georgia suspects discussed setting up specialized equipment to manufacture ricin. One of them, a former lab technician at the Agriculture Department, allegedly obtained castor beans.

There’s little description of the Georgia suspects’ motives in the court documents, other than a general contempt for the U.S. government.

One suspect allegedly compiled a “bucket list” of victims to target. The suspect, Frederick Thomas, told other members of the group, including an undercover FBI informant, that the politicians and others named needed to be “taken out” to “make the country right again,” according to a criminal complaint.

Thomas also allegedly raised the possibility of modeling the group’s attack on “Absolved,” an online novel that was written by a former Alabama militiaman and that centers on the fallout from a botched federal raid.

Thomas’s wife, Charlotte, reached by an Associated Press reporter, said the alleged plot was “baloney.”