The Key under the Door-Mat

František Schade from West Germany, now called Franz, pays a visit to his former schoolmate Pepíček Hlásek. Pepíček is fond of the bottle, and shortly after his friend's arrival, he organizes a spree, inviting girls. Pepíček is an easily gullible person, having no idea about Franz being a spy who wants to steal the documentation about a new invention of the chemist Vávra. His only reason to see Pepíček is the fact, that he is Vávra's neighbour. Vávra's family often go to their weekend house, leaving the home keys with Pepíček. After a cheerful party Pepíček immediately falls asleep, and Franz has enough time to take the keys and make copies of the documents at Vávra's cabinet. On the next morning Franz finds out that Pepíček is taking the research results to Vávra. Pepíček invites him to come along. Vávra's house is very cozy, full of antiques. Franz particularly likes a porcelain statue of a dancer. At the pleasant evening session, everybody gets dizzy, except Franz. He waits until everybody is fast asleep, and takes his time to make copies of the remaining documents. On the next morning, when saying goodbye, Franz promises to arrange an invitation for Vávras' to West Germany. He does not know, that Vávra's wife put the wrapped porcelain statuette into his car. The figurine attracts the attention of Czechoslovak customs clearance at the border. While searching the car, the officers find a spy camera, and so his espionage is revealed. The careless researchers face an unpleasant investigation.