Fatal Familial Insomnia is a genetic prion disease so rare that only a small number of families worldwide carry it, and this film lays out what happens once it activates. The mutation attacks the thalamus, the brain region that regulates sleep, and victims lose the ability to rest entirely, sliding through progressive insomnia into hallucinations, rapid weight loss, and dementia. There is no treatment and no cure: once symptoms begin, death typically follows within 7 to 36 months, usually around age 50. The film lays out the clinical progression and the certainty facing anyone who inherits the mutated gene, since FFI is passed down with near-total inevitability from parent to child. Without dramatization, it treats the disease as what it is, a stark case study in how a single misfolded protein can dismantle a fundamental biological function and, with it, a life on a fixed and known timeline.