Summer 1990. Elsa and her father go to the South of France on vacation. They meet up with old friends and their four children in a house lost in the hills. Immediately, the complicity between adults and children is rekindled. But Elsa senses a growing tension and secretly worries.
Five days before D-Day, the day of the last voyage of the Order of Sirius, a sect nestled in the Vaudoise Alps, Switzerland. Five days during which a community of 48 people, women, men, children, fed with esotericism and guided by a narcissistic guru, will test their faith and be deprived of their identity. Five days in which every gesture will be the last. Sirius is inspired by the massacre of the Order of the Solar Temple in 1994 in western Switzerland.