An epic water war is waged when the royal sisters babysit Flurry Heart after Twilight has to go to Ponyville, Shining Armor has been deployed, and Cadance needs a night out. After Flurry goes to sleep, Luna and Celestia resume the fight, but they decide to make it more interesting by turning it into a drinking game. Things escalate quickly when Cadance and Twilight join the war.