The intrigue of De Nachtegaal windmill

Jak and Bil invite Dinara to visit the Netherlands. Surprisingly, their visit to the museums is cut short by strange phenomena. Then, while wandering on the canals of Amsterdam, and when passing under a bridge, an envelope falls on their boat. Its content reveals secret information about windmills in the country. Before they even take interest, trouble begins. What did they do? What nightmarish plan will they discover when visiting De Nachtegaal windmill? They get drawn into a thrilling adventure in this country rich in culture and fascinating in its history...