Spoiler alert! The following contains details from Apple TV+'s "Lessons in Chemistry," through Episode 3, "Living Dead Things."

She's Elizabeth Zott, and this is "Supper at Six."

Actually, she's Brie Larson playing fictional chemist and TV host Elizabeth Zott in Apple TV+'s "Lessons in Chemistry" (streaming Fridays). Based on Bonnie Garmus' 2022 bestseller, the series follows a brilliant female chemist in the 1950s and '60s who faces discrimination and harassment, finds love, loses love, becomes a mother and, eventually, a TV star.

The book is a heartbreaking but uplifting story of a woman who survives unthinkable tragedy more than once. The series manages to capture the tone and themes of the book, but it isn't a carbon copy. Several key changes mark a departure in Apple's version. Here are the biggest, through the third episode of the eight-part miniseries.

Elizabeth's life at Hastings is (if possible) even worse in the series

The first episode of "Chemistry" succinctly illustrates the abhorrent sexism that permeates the culture at the Hastings Institute, the lab where Elizabeth and her eventual love interest Calvin (Lewis Pullman) work. The series ups the ante on the toxic workplace to get the point across faster than the book did. In the book, Elizabeth faces discrimination, is held back by her sexist boss and fired for being pregnant, but she is at least a full chemist. In the series, she is only a lab tech and later a secretary. The show also adds a "Miss Hastings" pageant to the story, where the women of the workplace are literally on display to be leered at by their male colleagues. It's not subtle.

Contrary to the book, Elizabeth works directly with Calvin and the couple attempts to submit her work for an important grant, although their efforts are ridiculed. In both the book and the show, Elizabeth's groundbreaking work is stolen by her boss, Dr. Donatti (Derek Cecil).

Changes to Six Thirty, the dog

The cuddliest character in both the book and show is Six Thirty, the oddly named dog who becomes a part of Elizabeth and Calvin's family. In both the show and book, Six Thirty (voiced by B.J. Novak) is trained as a bomb-sniffing dog but flunks out of the military. In the book, Calvin and Elizabeth adopt him together, but in the series Elizabeth takes him in before she and Calvin are together.

Six Thirty's name in the book comes from the time that he joined Elizabeth and Calvin's family, but in the show it's the time he wakes up Elizabeth in the morning. Overall, Six Thirty is less of a presence in the series, only given one internal monologue rather than throughout the story. In the book, he learns over 1,000 words in English, is charged with picking up Elizabeth's daughter from school and co-stars in the TV show she eventually hosts.

Calvin's death is subtly shifted

At the end of the second episode, just as his romance with Elizabeth has reached its peaceful pinnacle, Calvin is struck and killed by a bus while on a run with Six Thirty.

It's a slightly altered version of the way he dies in the book: There, he is hit by a police car desperately in need of a tuneup that's delayed by budget cuts. Six Thirty is less at fault in the book, spooked by a noise that triggers the PTSD he acquired as a failed bomb-sniffer. In the show, he simply refuses to cross the street. In both, the dog's leash, which Elizabeth buys, plays a pivotal role.

Harriet Sloane is an entirely different character

In both Garmus' book and the TV series, Harriet is Elizabeth and Calvin's neighbor, whom Elizabeth befriends after Calvin's death and the birth of her daughter. The big difference? In the book Harriet is white, 55, in an abusive marriage and has no community organizing efforts to speak of. In the series, she's played by 38-year old Black actress Aja Naomi King ("How to Get Away With Murder").

The series dramatically rewrote this character, who in the book mostly functions as a nanny, to make her a young, Black lawyer with an enlisted (and very kind) husband, two young children and a cause. She chairs a committee to block the construction of Los Angeles' Interstate 10, which would destroy her primarily Black neighborhood of Sugar Hill (in real life, the freeway was built and Sugar Hill destroyed).

In the series, Harriet is friends with Calvin before he even meets Elizabeth, while in the book, Harriet never really knew him. Show Calvin babysits Harriet's children, helps her around the house and bonds with her over jazz music.