Ned Stark and Littlefinger are colluding to deny the Iron Throne to the Lannisters and to pass it to Stannis Baratheon. The deal is that Ned, as the Hand of the King, provides political support and that Littlefinger, as the Master of Coins, ensures that City Watch supports their cause. If they both deliver they shall be successful. If one of them defects the other will be condemned as a traitor. Treason is punishable by death, while defector would be rewarded by the Lannisters. This puts them in strategic situation known as Prisoner's dilemma. Only difference is that one of them is driven by honour and vengeance, while the other is driven by instrumental rationality.
