Volume 1: Summer Joys
The little mole Mux lives deep underground. He has made himself comfortable in his home. But sometimes he doesn't want to be alone down there. Then he feels the pull to leave his home and go up to the sunlight. Just like on this summer day. He wants to visit his friends down by the river. Little does he know that a great adventure awaits him. But Mux wouldn't be a hero if he didn't manage to bring this exciting story to a happy ending. With the help of his friends, he succeeds, and the day ends joyfully for everyone.

Volume 2: Winter Magic
The sun is shining on the earth. It has snowed, and the snow sparkles on the fields. Deep underground in his home, Mux thinks it's time to check how things are outside. So he sets off and tiptoes over the snow towards the forest to visit his friends there. Soon he hears excited birds chirping. Something must have happened, he thinks. Indeed! A friend has found himself in a difficult situation. Mux has an idea. Can he save his friend with it?

Volume 3: Finally Vacation!
Deep underground in his bedroom, Mux the little mole wakes up and is wide awake. Vacation!, he exclaims happily. What should I do? He sits on his mound of earth and thinks. He doesn't have to ponder for long. His friends, the field mice, come by and ask him if he would like to join them. He gladly accepts the invitation. Soon the cheerful group reaches their destination: a magnificent farm. There is so much to discover. Danger for the little mice threatens from the farm cat, and Mux soon finds himself as the savior of a cheeky little mouse.