Feride, known for her mischievous and talkative nature, begins her story at school, reflecting on her past for an assignment. Her mother, Güzide, a Pasha's daughter, marries Captain Nizamettin. Due to her father's military postings, Feride spends her early years in various locations, cared for by Fatma and then Hüseyin after her mother's declining health. After Güzide's sudden death during a desert journey and her grandmother's passing, Feride is sent to a Catholic girls' school. Her rebellious spirit earns her the nickname "Çalıkuşu" (Wren), a name that sticks even after her father's death, leaving her an orphan at 12.

Feride spends her school years and summers at her aunt Besime's mansion. At 14, her 'cold war' with her older cousin Kamran continues. One evening, she overhears Kamran flirting with a recently widowed guest, Neriman, under a tree. Annoyed, Feride laughs, scaring Neriman away. Kamran, attempting to silence Feride, climbs the tree. Though they agree to keep it a secret, Feride later invents a love story with Kamran to impress her friends at school. Kamran's frequent visits, bringing gifts and sweets to prevent her from revealing his secret, only lend credence to Feride's fabricated tale. She feels a mix of pleasure from his visits and frustration, believing he's visiting Neriman before coming to see her. She is relieved when she learns Neriman has married and moved away.

Feride spends a summer in Tekirdağ with her aunt Ayşe and cousin Müjgan, who becomes her confidante. Feride confesses her made-up love story with Kamran to Müjgan. Müjgan, realizing Feride's true feelings for Kamran, tells Kamran about Feride's imaginary love life. During a swing ride, the rope breaks, and Kamran seizes the moment to propose marriage. They get engaged, but Feride avoids Kamran throughout their engagement. When she learns Kamran is going to Spain for four years, she encourages him to go, subtly upsetting him. Four years later, Kamran returns, and wedding preparations begin. Three days before the wedding, a mysterious woman visits Feride, showing her a love letter from Kamran to a woman named Münevver. Devastated, Feride writes a note to Kamran and flees, seeking refuge first with a relative's wet nurse, then with her mother's old nanny, Gülmisal Kalfa.

Feride, relying on her diploma, decides to teach in Anatolia to support herself. She disguises herself and applies for a teaching position, expressing her desire to go to Anatolia, which surprises the education director. Despite initial difficulties and a misunderstanding of her assignment, she is eventually appointed to a foundation school in Zeyniler. The journey to Zeyniler is long and arduous, and the village itself is a stark disappointment compared to her idyllic expectations. She finds the school in a dilapidated state, sharing it with Hatice Hanım, who acts as both janitor and teacher. Feride is disturbed by Hatice Hanım's harsh teaching methods and the solemn atmosphere among the children, contrasting with her own desire to bring joy and life to their education. She finds solace in the sound of a running stream, her student Vehbi, and especially a neglected orphaned girl named Munise, whom she eventually adopts.

Feride meets Military Doctor Hayrullah Bey when a wounded gendarme is brought to Zeyniler. Soon after, the education director inspects the school, deems it unsuitable, and closes it, leaving Feride without a position. A chance encounter with an old school friend, Christian Vares, who is married to a European journalist, changes her fate. She is appointed as a French teacher at the Darül Muallimat (Teacher's College) in B City, where she is loved by her students and colleagues, earning the nickname 'Silk Worm.' She settles in a new home with Munise and a pet goat named Mazlum. However, she faces new challenges, including the unwanted affection of Shaykh Yusuf Efendi, another teacher, whose feelings for her become public gossip. After his death, feeling uncomfortable, she requests a transfer to the Ç Rüştiyesi (Middle School) in a military town.

In Ç, Feride's beauty earns her the nickname 'Gülme Şeker' (Laughing Candy). She rejects a marriage proposal from Captain İhsan Bey. She is then tricked by a colleague into attending a dinner with influential officers, including Major Burhanettin Bey, and faints from distress. The school director helps her escape to İzmir. On the journey, she learns İhsan Bey defended her honor, leading to his court-martial. In İzmir, unable to secure a teaching post, she reluctantly becomes a private tutor, but leaves due to harassment. She finally gets a teaching position in Kuşadası, but her life is upended by WWI, which transforms her school into a hospital. She reunites with Doctor Hayrullah Bey and becomes a nurse. She aids İhsan Bey, who is severely wounded, and out of gratitude and pity, proposes marriage to him. He declines, unwilling to accept a marriage out of mercy. They part as siblings, and İhsan Bey returns to duty.

After five years and the war's end, Feride becomes the principal of her school. Doctor Hayrullah Bey retires. Munise falls ill and tragically dies, plunging Feride into a deep fever. Hayrullah Bey cares for her. Whispers and accusations of impropriety soon circulate about Feride and Hayrullah Bey. To protect her reputation, Hayrullah Bey proposes a marriage of convenience, promising to convert his çiftlık into an orphanage for them to run together. Feride, on the eve of their wedding, writes in her diary to Kamran, confessing her enduring love for him, which she realized only after their separation. Hayrullah Bey eventually dies, entrusting a package to Müjgan to give to Kamran after Feride's departure.

Meanwhile, Kamran, now a widower with a son, Necdet (whose mother was Münevver, whom he married out of a sense of duty after Feride left), returns to Tekirdağ, where memories of Feride resurface. He confesses his undying love for Feride to Aziz Bey. After 10 years, Feride arrives at the mansion. Kamran is stunned. Feride, unaware of his past, chats happily about his son. The household celebrates her return. After Feride offers Kamran a 'Gülbe Şeker' (Laughing Candy) she baked, demanding he confess his love for it, leading to a playful confession from Kamran. Late that night, Müjgan reveals to Kamran that Feride's husband died three months prior and delivers the package Hayrullah Bey entrusted to her, containing Feride's diary and a letter. After reading the letter and diary, Kamran understands everything. The next morning, when Feride attempts to leave, Aziz Bey stops her, revealing that Hayrullah Bey's letter and Feride's diary have been presented to the kadi, legalizing their marriage. Feride, with a cry and tears, is finally reunited with Kamran, who leads her to the spot where their story began. He declares that the 'Çalıkuşu' is no more, replaced by his 'Gülme Şeker,' sealing their love with a hug as a wren sings in a nearby tree.