Both House Stark and House Clegane were once-powerful and respected families, in their own rights. Now, both families have been disgraced: the Starks by the actions of several of the male family members, and the Cleganes by the mere existence of the sole surviving heir, Sandor. With little prospects for marriage and passing on their respective titles and lands, the heads of each family - Ned Stark and Anne Clegane - reluctantly negotiate a marriage between Sansa, the eldest Stark daughter, and Sandor.
Treated as a sort of public curiosity, the marriage between Sansa and Sandor is scrutinized. A large, ugly man marrying a disgraced king's delicate, beautiful daughter is bound to be full of dramatics to entertain the masses... right?