In a wooden hut used as a canvassing center, members of a children's puppet-theatre group are rehearsing for a production about a journey to the Moon. The goings-on inside the hut and outside are being closely followed by amateur detective Pepik Barnabás. He, however, is the first to be under suspicion when a trunk containing puppets goes missing. The children follow him but, when they catch up with him, they discover he hasn't got it. Pepík offers to help them in their search.