Ruby wakes Fini up and tells her that there is a problem with the rain. Although it´s pouring outside all the plants are dry. 
The two friends head out in the garden when the wind takes them and carries them up into the clouds. Up there they learn that there are different rain drops with different jobs on Earth. They need to find the plant raindrops and "fix the rain".
Like in every Fini and Ruby book the text is printed in two different colours which gives you the choice between two different versions of the story: a longer and a shorter one.