Plot
The story begins with Thatcher in the present experiencing dementia and seeing her deceased husband Denis with her as a ghost. In a series of flashbacks, the young Margaret Roberts works at the family grocer's shop in Grantham, listening to the political speeches of her father, whom she idolises; it is also hinted that she has a poor relationship with her mother, a housewife.
She wins a place at Somerville College, Oxford University. She struggles as a young lower-middle-class woman attempting to break into a snobbish male-dominated Conservative Party and find a seat in the House of Commons. She meets affluent businessman Denis Thatcher who is impressed by her eloquence and asks her to marry him; she accepts, but only after telling him she will not be satisfied to look beautiful at his side and be a mere housewife and mother: "I don't want to die cleaning a teacup."
Her struggles to fit in as a "Lady Member" of the House and as Education Secretary in Edward Heath's Cabinet are also shown, as are her friendship with Airey Neave, her decision to stand for Leader of the Conservative Party, her eventual victory, her voice coaching and image change.
Further flashbacks examine historical events during her time as Prime Minister, after winning the 1979 General Election, including the rising unemployment related to her monetarist policies and the tight 1981 budget (over the misgivings of "wet" members of her Cabinet – Ian Gilmour, Francis Pym, Michael Heseltine, and Jim Prior), the 1981 Brixton riot, the 1984–1985 UK miners' strike, and the bombing in Brighton of the Grand Hotel during the 1984 Conservative Party Conference, when she and her husband were almost killed. Also shown is her decision to retake the Falkland Islands following the invasion by Argentina in 1982, the sinking of the ARA General Belgrano and Britain's subsequent victory, her friendship with U.S. President Ronald Reagan aiding her emergence as a world figure, and the economic boom of the late 1980s.
By 1990, Thatcher is shown as an imperious but ageing figure, ranting aggressively at her cabinet, refusing to accept that the "Poll Tax" is unjust, even while it is causing riots, and fiercely opposed to European integration. Her deputy, Geoffrey Howe, resigns after she needlessly chastises him in a cabinet meeting. Heseltine challenges her for the party leadership, and her loss of support from her cabinet colleagues forces her to resign as Prime Minister after eleven years in office. A teary-eyed Thatcher exits 10 Downing Street for the last time as Prime Minister with Denis comforting her. She is shown as still disheartened about it almost twenty years later.
Eventually, Thatcher is shown packing her late husband's belongings and telling him it is time for him to go. Denis' ghost leaves her as she cries that she is not yet ready to lose him, to which he replies, "You're going to be fine on your own... you always have been", before leaving forever. Having finally overcome her grief, she contentedly washes a teacup alone in her kitchen.