On March 4, a former Russian spy named Sergei Skripal and his daughter, Yulia, were poisoned with a form of “Novichok,” a class of nerve agents whose variants can be up to eight times deadlier than VX, the potent chemical weapon that killed Kim Jong-un’s half-brother in October. “Novichok” roughly translates to “newcomer” or “n00b,” as the class of nerve agents is relatively new compared to other chemical weapons. Developed by Soviet chemists in the Seventies and Eighties, these nerve toxins are unique to Russian military and intelligence, which has led British and U.S. intelligence officials to suspect that Russia is to blame for the attempted murder.

The father and daughter were found on a bench near their home in Salisbury, England last Sunday. Both of them were unconscious. Shortly after Detective Sgt. Nick Bailey tried to help them, the police officer fell ill, too. His condition has since stabilized, but the Skripals remain in critical condition. UK investigators announced on Monday that the culprit was a rare and deadly Novichok nerve toxin, and UK Prime Minister Theresa May announced Monday that it’s “highly likely” that Russia was behind the plot to kill the former spy, reports The Independent.

Modern nerve agents are notoriously deadly. In the case of Kim Jong-nam, who merely had VX smeared on his face and clothes, the toxin killed him before he could reach a hospital. VX can be deadly in tiny quantities, as Inverse previously reported:

It kills quickly, even after exposure to infinitesimal amounts. Death by VX, which is a clear, motor oil-like liquid at room temperature, can occur after breathing in 25 to 30 milligrams, or just 10 milligrams if it comes into contact with the skin.

This is an incredibly small amount. If you were shaking salt onto a dish, for instance, you might accidentally scatter 25 milligrams off your plate and not even notice it. But compared to VX, Novichoks can be even more potent. Specifically, Novichok-5 and Novichok-7 are about eight times more potent than VX, though all these agents have similar effects on thd body.

Novichok nerve agents block the action of acetylcholinesterase, the essential enzyme that catalyzes the breakdown of the neurotransmitter acetylcholine. Acetylcholine is essential for transmitting signals between your neurons and your muscles, and normally, acetylcholinesterase breaks down the acetylcholine after it’s been transmitted because too much of the neurotransmitter causes your muscles to flex excessively. And this is exactly what Novichoks do: By blocking the enzyme that breaks down acetylcholine, these nerve agents cause a victim’s body to be flooded with acetylcholine. This leads to convulsions, paralysis, and eventual suffocation.

Too much acetylcholine spells doom for the human body.
Too much acetylcholine spells doom for the human body.

As New Scientist reports, the “small amount that we know about these agents is based on reports from Russian chemist Vil Mirzayanov, who exposed the development programme in 1991.” Based on the knowledge intelligence officials gained from Mirzayanov, we know that Novichoks can be binary compounds, which means that they can be produced by mixing two less toxic, less suspicious compounds together right before using it. This makes it safer for someone to transmit the highly toxic nerve agent, and it also makes it easier for Russian intelligence to subvert weapons inspectors, producing the deadly toxin without raising suspicion.

It’s not totally clear whether Russia is responsible for the attack, as Al Jazeera reports that Russian media is rife with conspiracy theories saying this is a false flag attack by U.S. or British intelligence agencies. But no matter who’s responsible, the fact remains: Novichoks are scary as heck.