Autist Daan sees the world very differently from his little sister Millie. The day begins normally, but when Daan accidentally kills Millie's bird, it triggers a chain reaction of feelings in the two children.
Bound by an unbreakable promise, Lu and Ika pledge to remain inseparable. But as they step into the opulent world of the Prussian court through their marriages, their oath faces a formidable trial.