After wrapping his acclaimed HBO series How To with John Wilson, John Wilson set out to make a documentary about concrete, the ubiquitous material made from sand, gravel, and minerals. You mix it with water and use it to create foundations, buildings, cities. As the project is developing, Wilson realizes the subject may not hold an audience. So he takes a workshop on how to write and sell a Hallmark movie and borrows its formula for his own. What began as a film about concrete morphs into Wilson’s struggle to balance creative ambition against the demands of the film industry. —Clara Scholl