Two friends are having a sleep over, one is extremely buxom and the other plain and flat chested. While rummaging through the fridge the flat chested girl discovers some milk in there and drinks it. When she mentions it to her friend she gets embarrassed and admits it is actually her milk and that is why her breasts are so large as she has to milk them regularly or they grow. Over night the flat cheasted girls breast grow over night a little and when she wakes up she is excited to see the change. Meanwhile the other girls milk pump breaks and she has started to get engorged with milk. The other girl thinking it must have been the milk that helped her grow decides to help her friend by drinking her milk from the source to help empty her breasts. That night the girl grows to at least the same size as her friend or bigger and starts lactating herself. The next day she is excited to show her friend her changes. They then decide that there are other girls at school that could use a boost so they decide to bake some cupcakes using their milk to give to the students and staff. The results are a lot of sexy students.