Hannah, Lisa, Sarah, and Sofia go on a day ride into the mountains with their horses. When a storm suddenly approaches, they are unable to make it home before dark and seek shelter in a cave. Naturally, the friends are curious and decide to explore the cave. Deep inside, they actually discover paintings of people and animals on the walls. Could these murals be from the indigenous people who are said to have once lived in the mountains? The four can hardly wait to tell their parents about their find, but the storm shows no signs of letting up, and they are stuck in the cave. When Lisa also injures herself while climbing, the situation becomes more critical. However, Hannah's father has already assembled a search party.