In May 1940, the opposition Labour Party in Parliament demands the resignation of British Prime Minister Neville Chamberlain (Ronald Pickup) for being too weak in the face of the Nazi onslaught. Chamberlain tells Conservative Party advisers that he wants Lord Halifax (Stephen Dillane) as his successor, but Halifax does not feel the time is right. Chamberlain is forced to choose the only man who the opposition parties will accept: Sir Winston Churchill (Gary Oldman), the First Lord of the Admiralty. Churchill tries to dismiss his new secretary Elizabeth Layton (Lily James) for hearing him, which earns him a rebuke from his wife Clementine (Dame Kristin Scott Thomas). King George VI (Ben Mendelsohn), who strongly distrusts Churchill, reluctantly invites him to form a government. Churchill includes Chamberlain (as Lord President of the Council) and Halifax (as Secretary of State for Foreign Affairs).