My Magical Pony: Sea Haze Book

Darcy, a friend of Krista's from school, leaves her dog with Krista to look after while she's away. Molly is a beautiful golden retriever and Krista loves her. She has a wonderful time with Molly, running her along the cliff path on summer evenings. But then Molly disappears! Everyone is involved in the search, but she is nowhere to be found. Krista rides out in search, feeling scared about Molly and guilty that she hasn't looked after her well enough for Darcy. She calls Shining Star, but he has urgent matters to deal with. Can he help in the search for Molly?