Frieda Petrenko is a fictional character from the BBC medical drama Holby City, played by Olga Fedori. She first appears during the twelfth series episode "Together Alone", originally broadcast on 17 February 2010. Frieda was introduced as a nurse, before retraining as a foundation doctor. She departs during the fourteenth series episode "Wolf's Clothing", originally broadcast on 15 May 2012. Frieda guest stars in a series 17 episode, originally broadcast on 22 September 2015, as a patient diagnosed with tuberculosis. Fedori reprised the role again in 2017 and returns in the nineteenth series episode "We Need to Talk About Fredrik", originally broadcast on 12 December 2017. The actress quit the role a year later and Frieda departs in the twenty-first series episode "Running", originally broadcast on 26 March 2019. The character received critical acclaim and Fedori earned a nomination for Best Newcomer at the 16th National Television Awards. Storylines Introduced as the cardiothoracic surgery ward's night shift sister, Frieda transfers to day shifts on the Acute Assessment Unit to cover the maternity leave of sister Chrissie Williams (Tina Hobley). Frieda has an initially antagonistic relationship with F2 doctor Penny Valentine (Emma Catherwood). When Penny learns that Frieda was a qualified doctor in her home country, Ukraine, she encourages her to retrain in the UK. Frieda resists the suggestion, but after being made redundant and having her diagnostic ability challenged by registrar Antoine Malick (Jimmy Akingbola), she decides to apply for an F1 position, which she achieves early in 2011. Throughout this series, Frieda and Penny grow closer, and Frieda’s affection turns from Penny’s brother, Oliver, to Penny herself. Frieda resolves to tell Penny her feelings, but on the morning she is going to confess, Penny is killed when the roof of a train collapses on her. Frieda faces many difficulties in her F1 year, including the death of her father, which sees her return to Ukraine. When Frieda returns to Holby, she bonds with new colleague, senior nurse Eddi McKee (Sarah-Jane Potts), over their dislike of new F1 Lulu Hutchison (Fiona Hampton), a daddy's girl, who is determined to prove she is a better doctor than Frieda. Frieda overcomes this competition when Lulu is transferred to another hospital; but again leaves Holby to return to Ukraine. It is revealed that she returned to Ukraine as her former mentor, Lev Tereschenko (Andrew Franchuk), is ill with a serious heart condition. Whilst