A bank is robbed by an invisible man. Outside, Clark sees the bank itself vanish from view, and soon after reappear. Later, all the water in the city ceases to flow, and it turns out Luthor, within an invisible helicopter plane, has somehow destroyed or removed the machinery from the city's pumping station. He threatens that not another drop of water will flow in the city if he is not paid one hundred million dollars the next day.

Clark communicates this demand to the mayor, who agrees, but secretly intends to pay with fake money. Superman brings the money to Luthor, buy by the time Luthor discovers the trickery, Superman has already followed him to his base of operations. There, Luthor has brought the money to a man named Bob Dunning, who has been involved in a fake stock manipulation scam with Luthor.

Luthor escapes, but Superman brings Dunning to the police, where he confesses his crimes.

Notes

Apparently, talking is a free action, because Superman is really hanging in the air for a long time while having that conversation with Luthor. Or maybe he's leaping repeatedly.

Upon further investigation, it seems that he is, in fact, flying, because Nowak didn't realize that Superman couldn't fly. Way to go with the research, there. Though I think that Superman had been flying in the radio show before this, so it's a legitimate mistake to make.