Forty years ago, a young Montreal Gazette journalist named Henry Aubin explored a city in perpetual development and the forces that were shaping it in his landmark book City for Sale.

Aubin is the central figure in Cities Held Hostage, a new documentary that draws on his investigative journalism from the 1970s.

The documentary uses Montreal as a case study of urban development in North America.

Director Martin Frigon reveals how colossal real estate fortunes have been amassed through a system of government contracts awarded to steel, concrete and construction companies.

The documentary uncovers the under-reported history of the deals and decisions that have shaped our built environment.

Frigon examines our changing attitudes toward architecture, our tastes and tolerance for density, gentrification and suburban sprawl, and the environmental impact of growth.

Cities Held Hostage calls for the protection of the places and landscapes that Montrealers consider an integral part of their identity.