“It’s all right, Eyvind,” said Somerled. “You don’t need to know these things. It’s different for me. To be what I must be, I have to learn everything. Reading, writing and games, archery, rowing and skiing, probably even smithcraft. And I must not forget music and the fashioning of verses. Without the mastery of these, a man cannot call himself a leader. And I don’t have long.”

Eyvind sat back, round-eyed. He said nothing.

“You don’t believe I can do it.” Somerled said flatly.

“On the contrary.” Eyvind spoke in tones of awe. “I’m beginning to believe you can do anything you put your mind to.” He watched as his friend carved the last rune and lowered the knife. “It looks very fine,” he added.

Something in his tone caught Somerled’s attention.

“What is it?”

“I—” Eyvind was unusually hesitant. “I’m wondering if—”

“What? You want to make your mark here too? You should, brother, for this belongs to the two of us. Our secret.”

“I would like to learn how to make my name. Properly, in these signs, not just a cross. It looks difficult. I’m not sure if I could do it.”

“We’ll practice it here, on the boards, until you have it. Then on the tree. Get your own knife and copy me.”

Eyvind was to remember, in later years, how patient Somerled was with him that day, talking him through each upright, each cross-stroke, letting him try it slowly, correcting each error with kindness, until Eyvind could inscribe a passable version of the runes that made his name on the bole of the great tree. For the space of that lesson, it seemed to Eyvind that Somerled became a different boy, one who could find joy in sharing what he knew, one who could give as well as take. It was a brief enough time, but Eyvind never forgot it.

Much later, after Somerled had returned to the south, Eyvind would climb up to the tree house sometimes and study the inscription in the bark. He would run his finger over the signs, just the part of it he knew said Eyvind, for the rest of it he was not able to decipher. It seemed to him a proud thing for a man to be able to write his name. As for the other part, that stood as a reminder of the vow he had sworn, for in those runes Somerled had set down the pact between them: two brothers.