The eye of midnight

Cousins William and Maxine arrive on the doorstep of Battersea Manor in May of 1929, to stay the summer with their grandfather, whom they hardly remember. Before they even get settled in, though, Grandpa, or Colonel Battersea, receives a cryptic telegram and takes them to New York to pick up a mysterious parcel. Before they get the parcel, Grandpa disappears, and the cousins meet Nura, a girl from Turkey who seems to know a lot about Colonel Battersea and the importance of the parcel--and she needs their help to stop a secret society of assassins and a group of cold-blooded gangsters from getting the parcel first.