.A spring of water known for its healing powers reached the swampy place where soldiers from the 30-year war in the 17th century lay. Next to it there is a new camping site with students from all over the world.

SYNOPSIS:

On the occasion of the 30th anniversary of the socialist youth convention, the activists decide to organize a summer holiday convention similar to the one in the past. Students from many countries will be invited to the convention somewhere in the countryside, everyone will be under control, there will be no night roaming around the city.

But it is the party that chooses the area - this place near the monastery known centuries ago for its miraculous healings, because under it was a spring with miraculous water. The monastery is the largest Cistercian abbey in the world. Now is abandoned.After the war the spring dried up and pilgrims stopped coming, but recently a rumor has surfaced that there is a linden tree on the monastery grounds whose bark heals teeth. The authorities try to fight superstition, but the folklore of the time claims that amalgams that dentists seal teeth with are poison. One of them pulled out a tooth with a crown and claims that a piece of wire in the tooth was not used as a reinforcement but as an antenna.

The party hopes that the event will drive away the pilgrims. Television arrives, there are silly talks and speeches, but in the evening there are games. One of the students thinks that the spring has dried up due to land reclamation. He looks into the drainage well out of curiosity and notices that garbage (bottles, wood and plastics) are thrown in by the students of the event.He fears a flood of water but no one listens to him

The boy is right, because by clogging the manhole the water is getting sideways into a small swamp, where the bodies of soldiers from the 30-year war are lying.

Oh no," says a student from the Czech Republic, "these are the Lisovci with which mothers in the Czech Republic still scare their children. To confirm his words he takes out of the monastery library an album with Rembrandt's works - one of the paintings depicts such a soldier.

They will not deal with them so quickly, they are warriors who used to trap their enemies like the Tartars and Cossacks.......