Crown of acorns / Catherine Fisher.

A teenage girl with a past arrives in a city: new name, new identity, new foster family. She has chosen the city herself, and is fascinated by its harmony and beauty, but is clearly in fear of being discovered. She is nursing a secret from her early childhood, a secret that produces new terrors for her the moment she fears her identity has been spotted. A parallel narrative is that of a young architect's apprentice, Zak, in 1750 working with Jonathan Forrest, a man obsessed with past Druidic mysteries, and with a new architectural vision for the city. He plans to create the world's first circular terraced street, the King's Circus - a plan greeted with scorn and derision. But Zac soon realises there's more than just an obsession with an architectural vision; some secret associated with the building of a hidden chamber in the centre of the Circus.