The series follows the careers and personal lives of four fictional British politicians, with each vying to become Prime Minister.
Four newly elected MPs take their seats in the government: Andrew Fraser, Scottish Labour member, whose father was a Conservative MP; Raymond Gould, middle-class lawyer and Labour representative; Charles Seymour, wealthy Conservative with a chip on his shoulder; and Simon Kerslake, ambitious Tory and longstanding Seymour rival.
The Labour party retains power after the general election, and the MPs are promoted. However, private turmoil disrupts three of them. Seymour is arrested for drunk driving, Gould engages a prostitute with potentially ruinous results, and Fraser and his wife endure personal heartbreak.
Gould puts his career on the line when he insists the government will not devalue the pound. Kerslake confronts Gould about the economic rumors and gets offered a post that rankles Seymour, who, in turn, is invited to become a Whip but would need to give up his privileged bank job.
Kerslake is appointed to a high position in the new Conservative government, but changing boundary divisions imperil his seat. Seymour does everything within his power to ensure Kerslake loses his place, while further advancing his own interests.
The MPs face shifting personal and political climates. Seymour ruthlessly bargains for a spot on the board of his family's bank while also repairing his marriage. With the government changeover, Kerslake, nearing bankruptcy, must leave Westminster; Fraser battles Scottish nationalists for his seat; and Gould becomes a member of the Queen's Counsel but alienates his wife.
The Labour party wins the general, and Kerslake accepts an offer to be the opposition's minister for education. However, Seymour plots financial ruin on the Kerslakes. Gould and Fraser also receive ministerial appointments, but the latter soon suffers a devastating loss.
Marital strife envelops two of the members, as Seymour discovers his wife's infidelity and Gould's wife meets his mistress. In the political realm, Kerslake's success continues. With the Tories back in power, he is appointed Secretary of State for Northern Ireland.
Kerslake endures constant surveillance and threats on his life in Northern Ireland. Fraser experiences drama of his own as changes within his party threaten his political future. Meanwhile, Gould attempts to reconcile with Joyce, and Seymour learns his new wife is less than desirable.
When Libyan dissidents capture a British navy vessel, the government scrambles to find a solution to the crisis. As foreign secretary, Seymour champions a diplomatic approach; defence minister Kerslake opts for a more dangerous but decisive military course; Gould's inquiry into the event earns him notice; and Fraser ascends to leadership of the Social Democrats.
Kerslake and Seymour duel for leader of the Conservative party, but one suffers a blow that changes his perspective on politics. A general election is called and two MPs are in the running for prime minister — with the third holding the deciding vote.