Awaiting good news from the IRS, Rhoda picks up the morning mail. She does indeed find a refund check for 18 dollars. (Unfortunately, she paid a man 25 dollars to prepare her tax returns.) There's also a letter for Mary in the mail, a chain letter Mary wants to throw away immediately. But then Rhoda points out that the letter was sent by Lou Grant.
At the office Mary discovers that both Murray and Ted received a chain letter too. Murray has already taken the office Christmas list to find addresses for his twenty letters. Annoyed with the hassle and the superstition, Mary rips up her letter and throws it away. By accident Lou finds the torn letter and tapes it back together. He convinces Mary to continue the chain after all. Not only can Mary earn $25,000, she will join the ranks of some famous people. Lou's broadcasting hero, Allen Ludden, is on the list.
At home, Mary looks through her address book to find twenty people she can send the letter to. She eventually picks some people she has met only once.
A few days later, Lou can show his colleagues that he has already received one dollar. Armond Lynton, a guest Rhoda once brought to a party, shows up at the office, believing that Mary's chain letter was an invitation to renew their friendship. As he keeps mentioning that he has divorced his wife and that it is his birthday, Mary can't help but accept his invitation to dinner.
That evening, Lynton arrives early at Mary's apartment. Rhoda offers to take Mary's place, but before that can be arranged, another visitor appears at the door. Traveling salesman Roy Martoni also got a chain letter and took it to be an invitation to sell some more stuff to Mary. He demonstrates his waterless cookware. Strangely, it's Armond Lynton who shows interest in the product. He buys up everything so they can all go to dinner.
Some time later, Ted proudly shows the letter that brings him his first dollar. His joy is short-lived: the letter is the one he sent to the person on top of the list. He forgot to put a stamp on the envelope and it was returned.