The four seasons of Diagnosis tell the story of Anna Leśniewska, a doctor who, after a few years of living abroad, returns to the country with a purpose of getting back her kids, taken away from her by their father. The series takes place in a hospital in Rybnik, and revolves around the lives of  doctors and nurses from the hospital  

In season 1, Anna has an accident, which results in memory loss. She is admitted to hospital, under the care of Jan Artman, who is the chief of the ward, as well as her ex-husband and the father of their children. Doctor Michał Wolski helps her with regaining health and memory. As a result he starts to develop feelings for Anna. Professor Artman is a tough player: intelligent, cunning, calculating. He’s willing to go to any lengths necessary to stop Anna from destroying the stability he’s built over the years, even to the point of committing a crime.

In season 2, Anna Leśniewska is onto a pharmaceutical company that tampers with research results of a new drug. Her private investigation leads to the head of the company being convicted for his crimes. However, it’s too late to help the victims of the drug. In season 3, professor Artman faces the demons of his past, one of which is doctor Bogna Mróz. Anna discovers the crime in which she was implicated by Mróz and Artman a few years back. Season 4 is the final resolution. Violence and vengeance build up. The lies and crimes concealed for years explode destroying the lives of the doctors in Rybnik. There are no winners and heroes. Anna pays a high price for her honesty and integrity.