Lulu and Snow White are about to jump over a fallen tree when Snow White's distracted by something shiny inside the nearby tree trunk. It's an old glass jar - nothing special, thinks Lulu. But then she sees there's a letter inside! She saves it until she can show it to her Pony Pals. The note dates from 1918, and it's from one ten-year-old girl to another. The Pony Pals try to figure out who the girls were and why they had to hide notes in an old jar to keep in touch. Soon they uncover the story of two long-ago Pony Pals, kept from each other and their ponies by an influenza epidemic. Eventually Lulu, Pam and Anna track down one of these girls, now an old woman, and restore her favorite pony-riding field to use.