That evening, Eddard searched carefully through the study in the Tower of the Hand.
At last, in a corner of the highest shelf, he found the book, The Lineages and Traits of the Noble Houses of the Seven Kingdoms.
It was a thick volume, and its parchment pages had already yellowed.
When Eddard turned to the chapter on House Baratheon, he found notes Arryn had left in the margins.
"Traits of House Baratheon: black hair, blue eyes. Since the War of Conquest, every member of House Baratheon, male or female, has possessed these traits."
Eddard kept leafing through the book until he found the chapter on House Lannister, which also bore Arryn's notes.
"Traits of House Lannister: golden hair, green eyes. Records of marriages with House Baratheon: Genna Lannister (golden hair) married Robert Baratheon (black hair). Traits of their offspring: black hair, blue eyes."
Several more examples followed. Regardless of whether the man or the woman belonged to either house, the children of these marriages invariably had black hair and blue eyes.
The notes ended there.
But Eddard already understood what Jon Arryn had meant. A chill crept up his spine and into his skull.
Robert and Cersei's three children, Joffrey, Tommen, and Myrcella, all had golden hair.
Before, he might not have understood what that meant. But after Petyr's warning, he had already guessed the truth.
"No," Eddard murmured to himself. "That's impossible."
But he remembered what Robert had said in the crypts of Winterfell. "Jon uncovered something. I don't know what, but he did. Now he's dead, and at such a convenient time."
That night, Eddard could not sleep.
He stood before the window, gazing at the lights of the Red Keep, his heart torn.
If Jon Arryn's suspicions were true, then Joffrey was not the lawful heir