[Note: No Breaking Bad spoilers.]

What is it and where does it come from?

Like some other scary poisons, ricin is naturally occurring. It’s a protein found in Ricinus communis, the castor oil plant. It can be extracted from the waste materials (the “mash” or “bean meal”) left over from castor oil processing and turned into a powder, pellet, or mist.

What does it do, and how bad is it?

Ricin kills cells by shutting down their ribosomal RNA, part of the molecular machine that builds their proteins. As the cells die, a ricin poisoning victim experiences different symptoms depending on how they were exposed, usually starting within 6 to 12 hours.

If the ricin was inhaled, the victim is in for difficulty breathing, chest pains, coughing, nausea, a buildup of fluid in the lungs, and respiratory failure. If the poison was ingested or injected, the victim can experience diarrhea, bloody vomit and urine, seizures, and failure of the kidneys, liver, spleen and/or heart. Death from organ failure follows within 36 to 72 hours of exposure, according to the Centers for Disease Control.

It doesn’t take much of the stuff to wreak this kind of havoc either. The lethal dose for an adult is around 0.35 to 0.7 milligrams by inhalation (less than the mass of a single grain of sand) and between 1 and 20 mg per kilogram of body weight by ingestion (1mg/kg is about what you’d ingest if you ate a small handful of castor beans).

Yikes. How do you treat ricin poisoning?

There’s no known antidote for ricin, so the best treatment is flushing it out of the body as quickly as possible while maintaining organ function and treating individual symptoms.

Scary stuff. What is it good for besides terrorizing politicians?

Biomedical scientists have been experimenting with ricin as a cancer treatment for decades. The ricin protein is linked to an antibody to form an immunotoxin that attaches only to specific, targeted cells. Once the immunotoxin latches on to a cancer cell, the ricin does its thing.

Other than that, though, ricin is mainly for murder and mayhem. Maybe the most famous ricin victim was Georgi Markov, murdered in a scheme that seems right out of a spy novel. In 1978, the Bulgarian writer was waiting for a bus when he felt a stinging pain in the back of his leg. When he looked behind him, he saw a man with an umbrella. The man crossed the street, got in a cab and fled. Three days later, Markov was dead, murdered via a ricin-filled pellet injected into his leg by the modified umbrella.