When scientist Mum needs some orange rocks for her experiments, Cosmo and her Dad travel to the searing hot planet Mercury to find some. Cosmo wants to search for the rocks right away but Dad has other ideas – he wants to enjoy the sunshine! Before long, they both fall asleep under the hot sun. When Cosmo wakes up, all is dark and cold. Dad's suit is completely frozen. Cosmo must head back to the rocket ship on her own to find a way to warm Dad up so they can complete their mission.