Kaylee was just drifting off to sleep when she heard it, an organic hum in counterpoint to Serenity's mechanical song. More puzzled than worried, she rolled out of her hammock.

She found River standing in a shallow alcove, her head tilted back, her eyes closed.

Before she could speak, the other woman opened her eyes. "I don't need to learn a language to sing it."

"I know a few songs if you want."

"Can you teach me the songs Serenity sings?"

"I can try." She took River's hand and pressed it to the bulkhead. "You have to listen very careful-like."