Ylva is a handsome young man, tall enough that door lintels make him duck, with a long, steady stride that still surprises him. His face is clean-lined and watchful, his jaw broadening into a stubborn point. He breathes through his nose in slow, measured pulls, but when rattled his breath catches with a dry click at the back of his throat. His teeth are very white and slightly pointed at the canines; he hides them when nervous, then shows them in a sudden, startling grin at a good risk. His gaze can go so cold and motionless that people check whether he is still breathing.

Bold and sociable, Ylva is drawn toward peril because it gives him something immediate to understand. He can be brisk and practical when others panic, yet unexpectedly tender when someone admits fear. He finds parts of his transformation fascinating, especially the strength and the strangeness of the new instincts, but that wonder can wound friends who experience the same crossing as loss. When relaxed he jokes freely; when ashamed he becomes all business, and when angry he is surprised by how quickly his body seems ready to act.

Before the crossing, Ylva was an American woman who worked as an emergency-department radiology technician. She misses the hum of the scanner, the certainty of protocols, and a small apartment where she had left a half-watered basil plant. The crossing dropped her into ninth-century Sweden in the body of a young man, with the local language and an unfamiliar life already pressing in. At first she treated the change as a problem to solve. Then, during a winter night when the displaced friends were trapped in a smoke-filled storehouse, she hauled a fallen beam off another survivor and realized that the new body's strength could be useful even when it felt alien. She accepts being male now, but still struggles with hunger that arrives abruptly, a libido she does not know how to read, and anger that rises faster and more physically than she expects. Ylva travels with the Seven Who Found One Another, a loose band of seven friends rather than a formal company. He is close to Tove, who shares his old-world displacement and misses her former life fiercely; their arguments often begin when Ylva admits that some changes fascinate him. He is also learning from Runa, a local fisher who trusts his curiosity but distrusts his strange silences. Their current problem is practical and dangerous: a household near the fjord believes the travelers brought a curse, while Ylva's uncontrolled venom has already left a dead goat and a frightened witness.