Plot synopsis: Two young physicists, engaged in the problems of atmospheric electricity and the study of thunderstorm phenomena, both disciples of Professor Dankevich, a talented, straightforward, incorruptible man, unwavering in his principles. Dankevich endeavoured to instil this uncompromising fight for honesty in science to the young scientists. And one of them, Sergey Krylov, lives up to the professor's expectations by continuing his work.