One explosion takes place in the lab of the research institute of a chemical plant. Emil takes the blame. The director of the institute orders the work on the case to be suspended. After his jail sentence, Emil equips a lab in the dwelling he is renting. A little before the end of experiments there is another explosion. Emil is in the hospital. A friend announces him that the experiment was a success. Next to Emil is the girl he loves.

The poor and illiterate village worker Dimo is in love with his landlord's daughter and events take their course...

A fishing boat comes back to the port. Fishermen are crestfallen, as they have caught only one very little fish. To save face, they fib they have 300 kilo of mackerel on board the boat. In their will to report a success, the port administration decides to pad out the weight. So, the very little fish is grossly exaggerated into tons of belted bonito, then into dolphin and ultimately, into a whale. Which results in celebrations, honors and awards... There, naturally, is no any whale. Instead of brilliant display of an unprecedented success, the white collars make a brilliant display of their unparalleled foolishness.

Professor Dimov is a diplomat who has been recruited as a spy by a foreign intelligence service. The suspicions fall on Dr. Belcheva. Major Kalinov is entrusted with the investigation of the case. He learns that she is Dimov's mistress. Paris, France. Dimov and Belcheva go out leaving a bag with secret documents in Belcheva's hotel room. Kalinov manages to retrieve the documents. After this incident Belcheva dies in hospital from poisoning. On board the plane Kalinov exposes the professor as a spy. Bulgarian counterintelligence officers arrest him.

Partisans hijack a boat