Watch The Madman of Lab Four for Free: How to Stream the Movie Online at 123Movies. . This talkative and unevenly paced feature finds Fou (Jean Lefebvre) the inventor of a gas that makes the users fall in love. He is chased by his boss, the police, and spies, who seek to secure the secret recipe for their own selfish purposes. A shadowy American underworld figure tries to intimidate the inventor. A half-hearted attempt at comedy tries to go along with the double dealing and trickery of the thin plot of the film.