Estella, born in 1950s England with a striking dual-colored hair due to a rare condition known as poliosis, finds herself on a journey marked by creativity and tragedy. At just 12 years old, she faces ridicule at school for her unique hair and rebellious spirit. Her mother, Catherine (Emily Beecham), recognizes Estella's potential and love for fashion, along with her fondness for a stray dog named Buddy. Seeking a fresh start, they relocate to London.
During a party thrown by Baroness von Hellman (Emma Thompson), Catherine leaves Estella in the car but, in a turn of fate, Estella chases after Buddy. This leads her to witness Catherine being tragically pushed by the Baroness's aggressive Dalmatians, ultimately resulting in her death. Believing she is responsible, Estella takes Buddy and escapes into the city, unfortunately losing her mother’s cherished necklace in the process. There, she encounters two street kids, Jasper (Joel Fry) and Horace (Paul Walter Hauser), along with their one-eyed dog Wink, who bring her into their fold as she changes her hair color to red.
Fast forward to 1974, Estella has grown into an adult, continuing her petty crimes alongside Jasper and Horace to survive while cultivating her passion for fashion design. When she celebrates her 22nd birthday, Jasper and Horace manage to get her a janitorial position at a prominent fashion store, but her artistic ideas are soon disregarded. A late-night shift leads to an encounter with the Baroness, who takes notice of Estella’s creative flair after a spontaneous window display makeover and invites her to join her prestigious team of designers.
As Estella’s career blossoms under the Baroness's mentorship, she befriends Artie (John McCrea), a vintage clothing shop owner whose taste inspires Estella further. However, when Estella spots her mother’s necklace on the Baroness, she is enraged and teams up with Jasper and Horace for a heist to reclaim it. Donning her natural color and adopting the alter ego Cruella, she disrupts the Baroness's event to execute her plan while unearthing dark memories, realizing that the Baroness had a hand in her mother’s downfall.
Cruella’s antics intensify as she steps up her revenge, flaunting eccentric outfits to mock the Baroness. She enlists the help of her childhood friend Anita Darling (Kirby Howell-Baptiste) to amplify her presence in the media. Tensions rise when the Baroness’s attorney Roger (Kayvan Novak) is dismissed and returns to his music career.
As Cruella’s schemes escalate, she continues to snatch the Baroness's Dalmatians, with one ultimately revealing the location of the lost necklace. The rivalry culminates in a dramatic showdown at a fashion show in Regent's Park, where the Baroness finally catches on to Cruella’s true identity. Captured and tied up, Estella orchestrates a fiery escape, leading to a tragic fall for Jasper and Horace who are wrongfully imprisoned.
Just when hope seems lost, John (Mark Strong), the Baroness’s valet, steps in, revealing shocking truths about Estella’s lineage. She learns that she is the Baroness's daughter, a revelation that fuels her thirst for vengeance against the woman who denied her the love of her true family. Armed with this knowledge, Estella fully embraces her Cruella persona, planning a final operation to topple the Baroness.
In a spectacular confrontation at a lavish party, Cruella brings the truth to light as she confronts the Baroness, leading to a dramatic push that results in the Baroness’s arrest, further aided by strategic planning from Jasper, Horace, and Artie. After utilizing a parachute to ensure her daring escape, Estella solidifies her status as the iconic Cruella de Vil, taking possession of Hellman Hall to establish her domain.
In a cheeky mid-credits moment, Cruella delivers two Dalmatian puppies, Pongo and Perdita, to Roger and Anita, hinting at the beloved tale of '101 Dalmatians,' with Roger composing a tribute song, "Cruella de Vil," in her honor.
