It's the year 2129. A long time ago a regression virus caused most of the world population to become helpless babies. The virus takes a week to fully regress someone, and makes those infected desperately wanna infect others to have other diaper dependent play mates. All those infected love diapers, using them, and having other people use diapers. You alone have discovered a cure to the virus, and must get it to the last human civilization that is free of the virus. You wake up in a nursery.