Shadowland: The Legend.

Frank (12) and his sister Caroline (16) arrive in mythical Attic Town in Shadowland, where the Great Syndicate is ruling and robbing citizens. An army of Shadows kidnaps anyone out after dark and the Patrolling Thieves make the daylight miserable for everyone. Attic Town is a place where the streets have no names and there is no turning back. Not realizing that they shifted in space and time, Frank and Caroline part, looking for directions. Wandering the streets, the boy meets Donlore, a young Patrolling Thief, and trusts this somewhat shadowy figure despite his first instincts. Caroline finds herself on a farm outside of town. She soon sets on a journey to find her brother and help him realize his mistake. She has to find him before dark. When the night falls, he will remain one of the dark rulers forever and there will be no way back. In the meantime, the underground opposition of Attic Town begins to revolt.