HBO’s miniseries Chernobyl, about the 1986 nuclear accident in the Soviet Union, is as “close to reality” as possible within a five-hour structure.

The Huntsman: Winter’s War’s Craig Mazin, who wrote and exec produced the drama, said, “We want to be as accurate as we can be. We never changed anything to make it more dramatic or to hype it up. The last thing we wanted to do is fall in to the same trap that liars fall into,” he said, speaking Friday at TCA.

Chernobyl, the first production under HBO and Sky’s fledgling drama partnership, stars The Crown‘s Jared Harris, Stellan Skarsgård (Avengers: Age of Ultron) and Emily Watson (The Dresser).

It dramatizes the true story of one of the worst man-made catastrophes in history and tells of the brave men and women who sacrificed to save Europe from unimaginable disaster. The miniseries focuses on the heartbreaking scope of the nuclear accident that occurred in Ukraine in April 1986, revealing how and why it happened and telling the shocking, remarkable stories of the heroes who fought and fell.

Harris plays Valery Legasov, the Soviet scientist chosen by the Kremlin to investigate the accident; Skarsgård plays Boris Shcherbina; the deputy chairman of the Council of Ministers and head of the USSR’s Bureau for Fuel and Energy; and Watson plays Ulana Khomyuk, a Soviet nuclear physicist committed to solving the scientific mystery of what led to the disaster at Chernobyl, so that it can be prevented from ever happening again.

The show is produced by Jane Featherstone’s Sister Pictures in association with Mighty Mint with Game of Thrones exec producer Carolyn Strauss executive producing. Mazin told Deadline that as a European story, it was important to have a producer like Broadchurch producer Featherstone on board.

“From a creative point of view, for me and for Carolyn Strauss, we knew we needed a European partner, we were telling a European story. Carolyn said we need a Jane Featherstone type and we figured Jane Featherstone would be the best Jane Featherstone type and we sent her the script and she was really excited about it. We immediately fell in love with her, she was very much the third part of our triumvirate. She has a wonderful team that works for me and has been invaluable.”

Kary Antholis, president of HBO Miniseries, said that Chernobyl was one of the “most compelling” pitches he’d heard in his 25 years in TV.

“[Craig Mazin said] ‘You think you know what happened at Chernobyl, but you have no idea’. Simple question: everybody knows it exploded but no one asks why. Chernobyl will be a horror movie, it will be a war movie, it will be a political thriller and a courtroom drama. You know how bad you think Chernobyl was? It was hours away from being much worse. The miniseries is everything Craig promised.”