It sounds like a fanciful script for a Hollywood thriller: foreign government agents plotting assassinations in the United States.

To be sure, there have been suspected state-sponsored killings in the past 20 years that have grabbed international headlines. Former Russian agent Alexander Litvinenko’s poisoning with a radioactive isotope in London in 2006 is one example; the murder of journalist Jamal Khashoggi at a Saudi diplomatic facility in Istanbul in 2018 is another.

And just this month, Maksim Kuzminov, a Russian pilot who defected to Ukraine after Russia’s full-scale invasion, was found shot dead in southern Spain. The Kremlin declined to comment on the case, but there are suspicions Kuzminov’s killing could have been a Russian-ordered assassination.

None of those took place in the United States. But in the past few years, there have been assassination plots aplenty in the U.S. In just the past 18 months, the Justice Department says it has foiled four of them on American soil.