Fitzgerald Fortune, a mean-spirited theatre critic and all-around jerk, is at a secondhand shop hunting for a birthday present for his wife Esther. He loves cruel pranks, and has decided that a player piano would be the perfect choice: Esther has been asking for piano lessons lately, so what better "gift" than one that implies she can't play? The brusque, gruff owner agrees to demonstrate the piano and puts a roll of soft music into it. To Fortune's surprise, the melody seems to have an effect on the man, as he reveals his hidden sentimentality and even offers to lower the price of the instrument. When the song ends, the shop owner comes out of his trance, as though it never happened. Intrigued, Fortune agrees to purchase the item and has it sent home.
At Fortune's palatial house, preparations are underway for Esther's birthday party. After offering the piano to his wife (and delighting in her instant understanding of the Stealth Insult), Fitzgerald puts a piece of cheerful music into the instrument. Suddenly, the house's incredibly somber butler Marvin enters and smiles uncontrollably. He explains that, despite his stoic demeanor, he loves working for Fortune—the man is so petty, and the drama he creates so hilarious, that Marvin's been laughing on the inside for years. The sudden flood of honesty yet again stops when the music does, and Fitzgerald realizes that the piano has the magical property of forcing people to reveal their innermost secrets when a particular tune is played.
Fortune decides to continue his cruel jokes by inserting a more violent song; this one affects Esther, who unleashes a lengthy tirade about how much she hates Fitzgerald, and that she views her marriage to him as the biggest mistake of her life. The critic is far more amused at Esther's humilation than he is insulted by her words, and keeps up the prank when Gregory Walker, a young playwright whose career he has impeded by writing nasty reviews, shows up. In moments, another song is playing on the piano, and Gregory is confessing his love for Esther. He even admits that the two had an affair when Fortune was away, sending Esther into a further tailspin of guilt—but she is even more insulted when Fortune reveals that he knew his wife was sneaking around with someone, and doesn't particularly care (he was more interested in finding out who she was seeing rather than why). Esther begs Fitzgerald not to use the piano at the party that night, but he refuses—he's having far too much fun to stop now.
The trio's conversation is interrupted by the first of the birthday guests to arrive: Marge Moore, a jovial, heavyset woman. A few hours later, the bash is in full swing. Marge is the life of the party, enjoying the food and company while cracking everyone up with some self-deprecating jokes about her weight ("Diet? What's that?"). Fitzgerald decides that Marge is the perfect target for the piano's magic and invites everyone to sit down as he demonstrates it. He chooses a piece that puts Marge into a trance, and she admits that she likes to imagine herself as a small, beautiful ballet dancer named Tina, going on to demonstrate some of her moves. The guests, thinking it's a joke, all laugh uproariously. But things take a turn for the serious when Marge begins dreamily revealing her secret hopes of finding a man to love her. Everyone realizes that she isn't kidding, and the laughter stops—save for Fortune, who is even more delighted when the song ends and Marge takes her seat, completely humiliated.
Fortune claims that he's saved the best for last, and instructs Esther to put a particular piece into the piano that he says will "bring out the Devil." Esther secretly swaps the rolls of music, and "Brahms's Lullaby" begins to play. The guests look around, trying to determine who will be affected—but it's Marge who notices that Fitzgerald himself seems oddly uneasy. She begins to ask him questions, and Fortune reveals his own hidden secrets. Deep down, he's nothing but a spoiled, scared little boy who lashes out at the world because he can't understand joy and love. He confesses to choosing his victims because of his own insecurities: he embarrassed Marge because he's envious of her genuine love of life, kindness, and ability to make others happy, while he attacked Gregory (and even wrote deliberately poor reviews of his plays) because he can't stand that the younger man has more creative talent than he himself ever will.
Marge, realizing that Fortune is "just a poor, frightened kid", takes pity on him and tells the guests that they should leave. As they silently file out, Fortune admits to hurting Esther most of all because he couldn't understand her love for him, and so attacked her like a child does. Gregory escorts Esther away, and Fortune is left all alone. He promptly throws a massive tantrum—"IF YOU LEAVE ME, I'M GOING TO BE VERY NAUGHTY!"—and destroys the whole room, including the piano roll, which breaks the spell and brings him back to normal. Marvin enters and sees his employer lying on the ground, surrounded by destruction. Fitzgerald angrily tells Marvin not to laugh at him, and the butler sadly promises just that: "I'm not laughing, Mr. Fortune. You're not funny any more."
- Acrofatic: When Marge is in trance, she demonstrates her desire of being a ballet dancer, and is very graceful for a woman of her size. This is Truth in Television, as Muriel Landers, who played Marge, was a gifted dancer.
- Big Eater: Marge samples every dish at the party with gleeful abandon. It's lampshaded when another woman remarks that she can't have a particular snack because of her current diet; Marge jokes "Diet? What's that?" It's one of the many signs of her genuine love of all of life's pleasures, as noted below.
- Big Fun: Marge is fun-loving and seemingly doesn't have a care in the world about her weight. It's at least partially an act, as her piano-induced confession reveals, but she is genuinely kind and has a great lust for life.
- Bittersweet Ending: Emphasis on the "bitter" part. Esther and Greg leave together, but it's rather treated as a retreat from the Manchild that Gerald truly is. This leaves Gerald to throw a humiliated tantrum, not just because his wife left him, but because his own true nature has been exposed. Even his own butler doesn't find him as amusing as before.
- Cannot Tell a Lie: This is part of the piano's power—if a question is asked while the right music is playing, the person under its spell has to answer it with complete honesty.
- Easily Forgiven: A variation. Marge, who suffered the most humiliation out of all of Fortune's victims (she confessed her deepest secrets in front of a whole room of people), doesn't gloat or try to get revenge on him when he shows his true colors. Instead, she realizes that he's a broken, scared child and implicitly forgives him, choosing to lead the other party guests in leaving rather than be petty. It shows both her maturity and Fortune's own miserable failings.
- Everybody Has Standards: Played with. It initially doesn't take effect when the party guests are laughing at an entranced Marge dancing and think she's joking. But once they learn these are her most genuine desires and secrets, all of them (sans Fitzgerald) go quiet.
- Fat and Proud: Marge, or at least, she pretends to be. She secretly desires to be thin, imagining herself as a dancer.
- Genius Bonus: Each of the pieces that causes people to reveal their hidden secrets matches the personality that they conceal:
- Throckmorton, the curio shop owner, is affected by "I'm in the Mood for Love," a sweet song about finding happiness just because the singer is near their lover.
- Somber Martin is changed by the musical theatre standard "Smiles," which naturally makes him break into uproarious laughter.
- Esther's tirade is set to "Sabre Dance," famously used in the ballet Gayane to demonstrate skill with actual swords—appropriate, given her rage and "cutting" words toward Fortune.
- Gregory Walker talks about his love for Esther when "These Foolish Things (Remind Me of You)" is playing; it goes well with both his deep passion for her and his claims that romance itself is "foolish."
- Marge Moore dances and confesses to Debussy's "Clair de lune." Not only is this song a gentle, dreamy standard, its title (which roughly translates to "Moonlight") reflects her delicate, beautiful soul.
- Fitzgerald's plan to "bring out the devil" uses the "Melody in F," known as one of the "Mephisto Waltzes," as composer Franz Liszt for a program about the Faust legend; Mephisto is short for Mephistopheles, the devil who features that work. The roll that Esther switches it for is Brahms's "Lullaby," a song frequently played for babies and small children; given that it makes Fitzgerald reveal that he's nothing more than a scared, spoiled, angry little boy, it fits perfectly.
- Genre Savvy: Fitzgerald recognizes the supernatural aspect of the piano's power almost immediately, and starts using it to his advantage within an hour of buying it.
- Hidden Depths: The Piano has the ability to reveal this in other people.
- Marvin appears perpetually sad, but it's meant to mask his jolly personality.
- Esther acts like a patient, complacent wife, but in reality buries a deep and passionate hatred towards Gerald's abusive nature.
- Greg pretends he's blissfully happy being a lonely bachelor, but turns out to be romantically in love with Esther.
- Marge secretly dreams of being a dancer, despite her round figure.
- Fortune is revealed to be a sad manchild who lashes out at everyone because he cannot understand love and happiness.
- I Just Want to Be Loved: This is Marge's deepest secret—she wishes that she could find a gentle man to take her into his arms.
- Ironic Echo: Early in the episode, Marvin the butler says that he's been internally laughing at Fortune and his petty games for decades. When Marvin enters at the end and sees Fitzgerald lying broken and humiliated on the floor, he remarks that he's no longer laughing—"you're not funny any more."
- Marvin kept his easily amused personality hidden because he was worried it would lose his job. However, up until the piano revealed it, Gerald was considering firing Marvin just because he seemed too glum and depressing.
- Similarly, Fortune makes a jolly game out of forcing everyone to reveal their hidden secrets — only to end up the most humiliated of all when he's subjected to the piano's magic.
- Jerkass: Gerald, in spades.
- Laser-Guided Karma: Fortune spends a whole day using the piano to make people blurt out all of their secrets...and at the episode's end, he's subjected to the same treatment, and abandoned by all of his friends and wife for it.
- Magic Music: The whole conceit of the episode—the player piano, when combined with the right roll of music, can make an individual start spilling out their deepest secrets and desires.
- Manchild: Gerald turns out to be this.
- My God, What Have I Done?: The party guests are wordlessly mortified that they laughed at Marge's wish to be a thin dancer when in reality, she was serious. What's more, they are left speechless at how genuine and sweet she is deep down.
- Perpetual Frowner: Marvin.
- Stepford Smiler:
- Marge, to some extent. She may be playful and seemingly takes her obese weight in stride, but it's all a façade to hide how poignantly she wants to find love.
- Marvin the butler is an inversion of this where he's a Stepford Frowner. At least, until the Piano reveals it.
- Esther is also this to a degree: she does her best to act polite and demure around Fitzgerald, but absolutely despises him and how he treats her.
- Sympathetic Adulterer: Esther. It's understandable, considering she's married to a man that utterly delights in making her miserable.
- Sympathy for the Devil: The kindhearted Marge quickly realizes that Fortune is a broken little boy trying to scare people and takes pity on him, leading the other guests in leaving without comment rather than seeking revenge. The immature Fortune takes this as an insult and throws a tantrum over it.
- Tomato in the Mirror: Of a "realistic" sort, and lampshaded by the end of episode narration. Fortune spends the whole episode exposing people for who they truly are, but gets his just desserts when he is revealed to have a deeply hidden personality.
- Your Cheating Heart: Esther has had an affair with Greg at least once. She tried to keep it a secret from Gerald, but he claims he already knew she was unfaithful.