It is the summer of 1929.  Cousins Maxine and William arrive at Battersea Manor, the home of their grandfather, Colonel Horatius Battersea, where they soon discover that Colonel Battersea isn’t the sort of grandpa who spends his afternoons napping on the porch swing.  When an ancient cult known only as the Hashashin descends on Battersea Manor, the cousins are swept up on a current of intrigue that leads from the hidden passages of the manor to the criminal underground of New York City. Maxine and William must navigate an adult world of mobsters and flappers, swindlers and vagabonds in a desperate bid to recover the elusive parcel and rescue their grandfather from the Hashashin.