A traveller comes knocking at the door of twelve-year-old Freya and her mother, seeking accommodation late one Sunday evening. Invited in for the night, Mr Amelin ends up staying with them for the next three months, although Freya can't work out the purpose behind his visit to their isolated village of Arnbrice.
Mr Amelin's arrival brings about intriguing coincidences and magical events, many of which help to make their harsh lives a little more comfortable. Mysterious children's voices are heard, unexplained gifts appear, and Freya wonders what is in the briefcase Mr Amelin carries around with him wherever he goes.
Freya and her best friend Harry, who suffers bullying treatment at the hands of his father, like to play in a secret garden they have created high in the hills. One day they are found out, and then it becomes clear that the traveller is there to help.