When Lillie spends the summer in Wales with her family, she can't help but feel like the baby of the group. Her big sister Frankie would rather spend time with their older cousin Lana than play with her, and no one else seems to notice how lonely she is.

Then during a boat trip, Lillie spots a young dolphin swimming alongside them and for a short while all her worries melt away. Later, when Frankie and Lana are particularly mean to her, Lillie decides to set off on her own in hopes of seeing the dolphin calf again ...