Martha Klein (Martina Gedeck) is a chef at Lido, a gourmet restaurant in Hamburg, Germany. A perfectionist who lives only for her work, Martha has difficulty relating to the world other than through food. Her single-minded obsession with her culinary craft occasionally leads to unpleasant confrontations with customers. Consequently, the restaurant owner, Frida (Sibylle Canonica), requires her to see a therapist (August Zirner) to work out her poor interpersonal skills. Martha's therapy sessions, however, turn into monologues on food, and her approach to stress management usually involves hiding in the restaurant's walk-in refrigerator.
Martha's life takes a dramatic turn when she learns that her sister died in a car accident, leaving behind a young daughter, Lina (Maxime Foerste). The girl's father, Giuseppe Lorenzo (Diego Ribon), has been out of the picture for years living somewhere in Italy. Martha must now look after her niece, who is depressed, withdrawn, and refuses to eat. While trying to cope with her sister's death and the difficulty of raising a young girl, Martha's world is further complicated when Frida hires funloving and unorthodox Mario (Sergio Castellitto) as a sous-chef to replace Lea (Katja Studt), who is expecting a child any day. Martha looks on in horror as Mario transforms her kitchen of precision and logistics with his relaxed banter and Italian music.
Unable to find an acceptable babysitter, Martha starts to bring Lina to the restaurant with her. Lina warms to Mario's playfulness and even devours a plate of spaghetti he's prepared. Touched by Mario's kindness and concern for the child, Martha becomes more accepting of Mario. She even asks for his help in locating Lina's father in Italy and translating a letter she's written to him.
Just as Martha's relationship with Lina seems to be improving, a setback occurs when she forgets to pick the girl up from school while helping Lea get to the hospital to deliver her baby. Lina is angry at being forgotten. To make amends, Martha offers to grant Lina any wish. For her wish, Lina wants Mario to cook for them. Mario agrees, and prepares a picnic-style dinner in Martha's living room. Despite the mess left behind in the kitchen, the evening of stories and games bring the three closer together.
Martha's relationship with Lina is tested again when Martha is informed by the school principal that Lina has not been attending school regularly, and when she does come to school, she sleeps in the classroom. Lina has also been telling her friends that she's forced to work in a kitchen for her room and board. Angered by Lina's behavior, Martha tells her she can no longer come to the restaurant. Lina storms off, nearly getting hit by a car, and later attempts to run away to Italy. A frustrated Martha tells Lina in frustration, "I wish I had a recipe for you, that I could follow." Mario continues to support Martha, and their relationship becomes romantic.
Lina's father finally arrives, and takes his daughter to Italy to live with his new wife and family. Distraught and conflicted by the separation, Martha rejects Mario's loving support, and after another confrontation with a customer, she quits her job.
Martha reconciles with Mario, and the two drive to Italy to bring Lina back to Germany. Martha and Mario marry, adopt Lina, and make plans to open their own restaurant together. Meanwhile, Martha's therapy sessions have turned into cooking lessons for her therapist, who is amazed that she can tell the difference between the type of sugar he used and the type of sugar called for in the recipe.