Little Max and his friend Tüte want to make the pharmacist into an April fool by asking him for a bottle of mosquito fat. But the pharmacist is clever and sees through the boys’ plan. He labels a bottle “Muscle Power for Cosmonauts, three tablespoons per hour.” Tüte wakes up little Max during the night because he is so excited to share his discovery: One sip from the bottle will turn anybody into a cosmonaut. Little Max drinks some of the tonic and immediately finds himself in full cosmonaut gear. Suddenly, both boys are in outer space, but the tonic has worn off and they are in their pyjamas. They urgently need another sip from the bottle. Or maybe it was all only a dream?