Dear Mister Moon (1998)

When two half-sisters, thirteen-year-old white-haired Sigrid and seven-year-old black-blooded Saara meet for the first time, it turns out that their common grandmother has been taken to a nursing home. The girls come up with the idea to steal him from there and hide him in the attic where they can be with her undisturbed. Everything goes well beyond expectations until drunkards, thugs and extortionists intervene and the girls have to act decisively to escape from them.