When people who attend a concert at Plymouth Hall are robbed, seemingly without their knowledge, Clark and Lois attend the next evening's concert to see if lightning strikes twice. It does, and Clark discovers that mass hypnotism is involved, which makes it all the worse a few nights later when the concert is broadcast over the airwaves, making people fall asleep while listening to the program, and allowing criminals to rob them blind.; Perry sends Lois and Clark out to cover a fisherman's story that he has spotted a living mermaid. Lois dismisses it after the interview, but Clark decides to investigate further and discovers the man is telling the truth. The mermaid tells the Man of Tomorrow that her father's evil adviser is planning to invade the land world and must be stopped.; Superman responds to a horrible lightning storm that is reeking havoc all over Metropolis; When young Chet Farnsworth's invention, a fire extinguishing powder, is successfully used to put out a tenement fire, the young man hastily signs a contract with an unscrupulous man, not realizing that he has just signed the rights and any profits away to him.