Alexander Litvinenko dies in a London hospital on 23 November 2006, poisoned with polonium-210, and before he goes he gives Scotland Yard a detailed account naming his killers. The trail leads to Andrei Lugovoy, a former KGB officer and later a member of the Russian State Duma, who becomes the British investigation's chief suspect but refuses extradition and denies any role in the murder. The film follows that investigation using Litvinenko's own testimony to police, interviews with people close to the case, and the international manhunt that traces polonium traces through London hotels and flights back to Moscow. It gives real weight to Lugovoy's response: a lie detector test administered in Moscow by the British Polygraph Association in 2008, whose results he says clear him of contact with polonium and involvement in the poisoning, and which British authorities dismiss as unverifiable and inadmissible. The film sits inside the diplomatic fallout that follows, tracking how one man's denial and one contested test helped freeze relations between London and the Kremlin.