Kind of like the Truman Show in reverse. A teenage brother and sister somehow manage to travel into the world of a 1950s TV sitcom, which exists in a black-and-white world. Naturally the 1950s value systems prevail in this community. The sister sets about changing that by introducing sex, and soon, the effects start to be felt wider and wider as more people become self aware. As this happens, their world changes from black and white to colour.