Three teenagers, Kat, Ned and Jay are caught trespassing on their school sponsor's property. Forced to miss the day of the school trip, secret technology sends the teenagers to the sixteenth century with a mission to find a metallic device. To help them locate the object they need to return home, they are given a compass that displays shadowy numerals. Upon realising that they truly have landed in Greenwich Palace in 1535, the three friends find help in the form of a youth called Kit, who gets them work in lowly positions within the Palace. As the three friends settle into a routine, not without incurring the bemusement and mirth of their new colleagues and friends, they realise that the device they seek is hidden within an inaccessible area of the Palace - deep within the King's Gatehouse, in the highest offices of the Privy Council. The world of 1535 is full of intrigue and danger...