LONDON — After a former Russian spy was found convulsing on a park bench in the English city of Salisbury, the British prime minister at the time, Theresa May, stood before Parliament and the world and accused the Kremlin of “a brazen act to murder innocent civilians on our soil.”

The March 2018 speech, in which Mrs. May revealed that the former spy, Sergei V. Skripal, had been poisoned with a deadly nerve agent known as Novichok, shook the British public and set the stage for a geopolitical confrontation that continues to reverberate two and half years later.

But in “The Salisbury Poisonings,” an engrossing and deeply researched four-part drama about the attack that premieres on Thursday on the streaming service AMC+, the speech is just background noise. It plays briefly on a blurred television screen before a character barks, “turn that [expletive] off.”