A tribe of cats called the Jellicles must decide yearly which one will ascend to the Heaviside Layer and come back to a new Jellicle life.
In the streets of London, a car stops near a building long enough to drop off a bag in the garbage. This is seen by a number of cats, who examine the bag. It contains a white cat named Victoria, who had been abandoned (Overture). The cats then question whether or not she is one of their tribe, known as Jellicles (Jellicle Songs for Jellicle Cats). One of the cats, known as Mr. Mistoffelees, befriends her. Three of the Jellicle cats stop Victoria and ask for her name. When she gives it, they ask for her second name, which makes Munkustrap explain the importance of the names of Jellicle cats (The Naming of Cats). She later is given an invitation to the Jellicle Ball, which occurs only once a year, where many cats compete, and the leader of the tribe, Old Deuteronomy, chooses which of them goes to a place known as the Heaviside Layer to undergo reincarnation (Invitation to the Jellicle Ball).
The Jellicle cats then take her to one of the candidates for the night's Ball, a cat named Jennyanydots, who sleeps during the day, but reforms mice and cockroaches at night (Jennyanydots: The Old Gumbie Cat). The next cat to visit Victoria is Rum Tum Tugger, a capricious and rebellious tomcat, who treats her and other cats to milk and cream at a milk bar. (The Rum Tum Tugger) After the well-appreciated drink, a dirty and life worn cat named Grizabella appears, only to be turned away. One of the cats explains to Victoria that Grizabella was one of their tribe until she went off with Macavity (Grizabella: The Glamour Cat). A new cat, Bustopher Jones, arrives and notes how underfed the new arrival is, and proceeds to take her and the Jellicle Cats around to the garbage bins of various restaurants for them to eat (Bustopher Jones: The Cat About Town). The merriment is cut short, however, by the arrival of Macavity, who had previously approached Jennyanydots and abducted her, goes on to kidnap Bustopher Jones next. The two Jellicles find themselves on a boat in the middle of the Thames, tied up and kept watch by one of Macavity's agents, Captain Growltiger (Growltiger's Last Stand). Meanwhile, the Jellicles all leave, with the exception of Victoria, who is left behind.
She is found by two mischievous cats and shown how fun a wild, carefree life can be (Mungojerrie and Rumpleteazer), who are unknowingly also agents of Macavity. The merriment and wanton destruction are cut short when the dog of the house starts coming after the trio. The duo leaves out the window, but Victoria, who is loaded down with pearls, a watch, and earrings, is caught on the bedpost and cannot escape. Mr. Mistoffeloees, who has been looking for Victoria, helps her get free and distracts the dog long enough to close the door and escape, bringing her to the others at an abandoned theatre. They are just in time to meet the leader of the Jellicles tribe, an old female cat named Old Deuteronomy (Old Deuteronomy). Once she arrives, the Jellicle Ball commences (The Jellicle Ball), with Mr. Mistofelees as Victoria's dance partner. While the cats are taking a rest, Grizabella reappears, but at a distance ("Grizabella The Glamour Cat - Reprise, Memory). This is not unnoticed by Victoria (Beautiful Ghosts) or Old Deuteronomy (The Moments of Happiness). Once Victoria is back inside, she speaks with Old Deuteronomy and tells her story. The elder cat says that Victoria is not a Jellicle Cat yet, but she is on her way to becoming one.
The first contestant called up is an old theatre cat called Gus (Gus: The Theatre Cat), who Mr. Mistoffelees, a big fan, helps out his act with magic. After his number is done, Macavity lures him into signing an autograph before kidnapping him as well. Next up is Skimbleshanks (Skimbleshanks: The Railway Cat), who is abducted in mid-act. Bombalurina, another of Macavity's agents, appears on stage and doses everyone with catnip (Macavity: The Mystery Cat). Soon after, Macavity himself arrives and tries to coerce Old Deuteronomy into choosing him for rebirth, which she refuses to do. Infuriated, he kidnaps her, then threatens her life. When she still refuses, Macavity starts to make her walk the plank. Victoria suggests that a less-than-confident Mr. Mistoffelees rescue the leader by conjuration (Mr. Mistoffelees). After a few tries, the Magic Cat manages to rescue Old Deuteronomy in this manner, to the relief of Victoria and the Jellicle tribe. Grizabella returns and is about to leave when Victoria stops her and encourages her to come and sing in the Jellicle Ball (Beautiful Ghosts (Reprise), Memory - Reprise)". The Glamour Cat is not only re accepted by the tribe, but she is also named the Jellicle Choice by Old Deuteronomy. The cats lead her to what looks like an old chandelier, which Mr. Mistoffelees repairs and lights up. The object rises into the air, revealing itself to be a hot air balloon (The Journey to the Heaviside Layer) as Grizabella rises into the air while dawn breaks. Macavity climbs on to a long tether, thinking that he would go with her, but falls off within moments. The Jellicle cats watch her from a statue outside as Old Deuteronomy addresses them all (Finale: The Ad-Dressing of Cats). They salute Grizabella before dispersing, leaving only Victoria and the leader, who declares her an Angelical cat, one of the types of Jellicle cats. Grizabella disappears into a cloud in the dawn, going off to be reincarnated.