One & Only is a work of contemporary romantic fiction by Maurene Goo. Originally published in 2026 by G. P. Putnam’s Sons, One & Only follows 39-year-old Cassia Park’s search for true love. Cassia works for her family’s business, One & Only Matchmaking, where she, her grandmother, and aunts read clients’ faces, enter their past lives, and divine who their soulmates are. Cassia has known her soulmate’s name for 10 years but has yet to meet him, only to fall for an attractive young man named Ellis, whose boss, Daniel Nam, is her fated love. Written from Cassia’s first-person point of view, the novel explores themes including Belief in Destiny as Both Comfort and Limitation, the Conflict Between Inherited Stories and Self-Authored Identity, and Personal Desire Versus Familial and Cultural Expectations.

Maurene Goo is the author of several YA novels, including Throwback and Since You Asked. One & Only is her adult debut.

This guide refers to the 2026 G. P. Putnam’s Sons hardback edition of the novel.

Content Warning: The source material and guide feature depictions of cursing, sexual content, substance use, illness, graphic violence, and death.

Plot Summary

Cassia Park is a 39-year-old businesswoman living in Los Angeles in the house where she spent her early childhood with her mother, Evette, who has since passed away. She works for her family’s company, One & Only Matchmaking, which uses an ancient Korean art of face-reading to divine clients’ soulmates, or fated loves. When Cassia was 30, her grandmother (or “Halmoni”) read her face and informed her that her fated’s name was Daniel Nam. Ten years later, Cassia still hasn’t found or met Daniel. She hopes that turning 40 will mark a turning point in her life.

The week before Cassia’s birthday, she takes a bike ride with her best friend, Marcella, at Frogtown River Park. She gets into a minor biking accident, and an attractive 28-year-old man named Ellis comes to her rescue. While waiting for paramedics to arrive, Cassia and Ellis talk and flirt. Afterward, Marcella teases Cassia about Ellis, urging her to give him a chance. Cassia insists that he is too young and reminds Marcella that he is not Daniel Nam.

A few days later, Ellis shows up at Cassia’s office to see if she is okay, having found her workplace via social media. Cassia is surprised and flattered, and the two go out for coffee. Ellis reveals his interest in Cassia. Although she reiterates their age difference, she can’t help feeling intrigued by the energetic, magnetic Ellis. Later, she tells Marcella about their encounter, and Marcella urges her to have some fun with Ellis while she waits to meet Daniel.

Cassia ends up inviting Ellis over that weekend. They have sex and end up spending several days together. Cassia is surprised and confused by how much she likes Ellis, careful to remind herself that they have no future. On the morning of her 40th birthday, she tells Ellis goodbye, explaining that she needs someone older and more serious. Then, she drives him to work on her way out of town for her annual solo birthday trip, which also marks the anniversary of her mother’s death. Outside Ellis’s office, Ellis introduces Cassia to his boss, Daniel Nam.

On her way to Joshua Tree, Cassia is reeling. She cannot believe that she met Daniel and that he has a connection to Ellis. After settling into her yurt, she tries to set the conflict aside and focus on her birthday and her mother. Evette died of a brain aneurysm on Cassia’s eighth birthday, and Cassia has never gotten over the shock of this loss. She always spends the day alone, still convinced that she is somehow to blame for Evette’s passing. Halmoni—as well as Cassia’s great aunt (“Emoni”) and her aunt Sunny—have led her to believe that because Evette married a man who was not her fated, she ended up alone, was overstressed as a single mother, and died.

The next day, Cassia runs into Ellis, Daniel, and their landscape architecture firm, Watson and Associates. They are in Joshua Tree for a company retreat. Cassia finds herself accepting Ellis’s invitation to join the group for a bonfire that night. They take mushrooms and drink wine. Cassia feels comfortable and at ease, suddenly unsure why she has felt so worried and stressed for so long. That night, she and Ellis spend time alone together. Cassia hears herself opening up about her mother and fraught past. Ellis is sympathetic and reveals that he married his high-school sweetheart and got divorced not long after.

Over the following days, Cassia spends more time with Ellis while also getting to know Daniel. She feels more confused than ever. She has a connection with Ellis, but her fated is right in front of her. Before the weekend ends, she officially breaks things off with Ellis—stressing their age difference and her desire for children.

Back in Los Angeles, Cassia tells her family about meeting Daniel, and together they decide to invite Daniel to their upcoming matchmaking event. At the event, Cassia finds herself taken with Daniel, convinced that they are indeed meant to be together. He is handsome, charming, and put-together and seems like the exact man she has always dreamed of.

Over the following weeks, she and Daniel start a more serious relationship. Cassia convinces herself that she is happy, despite Marcella’s constant prodding about Ellis, whom she knows Cassia really liked. Meanwhile, Cassia continues to run into Ellis around town. Whenever they see each other, the connection between them is palpable. When she tells Ellis about Daniel, he struggles to hide his hurt. He is especially upset when she informs him that she will be attending the wedding of one of his colleagues, Max, with Daniel.

At the wedding, Cassia realizes that she is frustrated with Daniel for pressuring her into attending the event. She feels awkward being around Ellis and all of his colleagues, who first met her when she was seeing Ellis. On the dance floor at the reception, she and Ellis end up expressing their interest in each other, but Daniel interrupts.

Back at home, Cassia dismisses thoughts of Ellis and invites Daniel to meet her family. At the dinner, Halmoni, Emoni, and Sunny are charmed by Daniel—prodding him with questions about his and Cassia’s relationship’s future. When Daniel reveals that he has no interest in being a father, the family is shocked. Afterward, Cassia struggles to reconcile with Daniel’s revelation. She airs the truth to Marcella, who suggests that she take time away from Daniel to get some perspective. However, Cassia has already committed to attending his opening at the park the next day; he and the firm have been redesigning Frogtown.

At the opening, Cassia runs into Ellis outside the bathrooms. They chat, and then Ellis professes his love for Cassia, inspiring a passionate kiss. Daniel discovers them, and a fist fight ensues between him and Ellis. Afterward, Cassia heads home with Marcella, venting about her confusion.

Sunny visits later and tells Cassia that she has something to tell her: Matthew, Cassia’s father, was Evette’s fated. Although they were meant to be together, Matthew still left Evette. The story they told Cassia all these years is wrong. Sunny apologizes, explaining that she wants Cassia to know the truth because she doesn’t want her to end up making the wrong choice. Even if she does choose Daniel, there is in fact no guarantee that they will live happily ever after. Sunny then gives Cassia Matthew’s contact information.

Cassia impulsively flies out to Detroit to see her father. The two catch up and explain themselves to each other. Talking to Matthew gives Cassia clarity. Back at home, she breaks up with Daniel and then confronts her family about the secrets they’ve been keeping. Then. she goes to see Ellis, telling him everything that has happened, explaining the concept of soulmates, and professing her love. Ellis appreciates her openness but says that he needs time.

Not long later, One & Only catches on fire during an earthquake. Cassia devotes the next weeks to company renovations, after which Halmoni passes the business to her. Then, one day, Marcella invites Cassia, her family, and Ellis to the opening of her new restaurant. Cassia and Ellis reconnect, make amends, and profess their love.

A year later, Cassia and Ellis have made a life together. One day, they get a call from the fertility agency where Cassia harvested her eggs, and the couple makes an appointment for implantation. That night, they celebrate with their family and friends. Cassia looks around the table, observes her loved ones, and feels her mother’s presence.