Fleur and Michael race to diagnose a patient who keeps arresting. However it becomes evident at the end of the day the surgeons are competing more than professionally. A soldier helps cool the strained relationship between Adrienne and Serena.
Zosia returns to the wards of Holby City, but her intensive behaviour forces Guy to ask for another psyche assessment on his daughter. Serena opens up to Raf about her feelings regarding her mother's death. Jac agrees to fund Elliot's protoype for the Herzig.
Zosia's friend, Lisa, encourages Zosia to stop taking her lithium tablets. Afterwards, Zosia treats a male patient, but ends up misdiagnosing him. Then, Lisa pretends to fake her illness to be discharged from hospital, but Jesse is unaware of her unstable condition. Serena argues with the chairman of Holby City.
Raf and Harry's working relationships improves, so Raf asks Amy for a divorce. However, when Amy later goes into labour she gives birth via cesarean. A confident Dominic asks Fleur to go on the Los Angeles list. Jac kisses Guy, while Mo struggles to hide her feelings from Jesse.
Zosia's creepy behaviour endangers her when she is insistent that a dying elderly female patient is her mother. Adele kisses Jesse, causing an awkward tension for Mo when she rejects Mr. T. Amy announces her plans to move back to Singapore.
Oliver Valentine is attacked by thugs outside the ED as he mysteriously returns. When he is rushed up to Darwin Jac discovers he has Chagas disease. Further problems occur as Oliver is also suffering from cirrhosis of the liver, making Elliot's hopeful heart operation tricky. He continues however, using his heart device he's been working on. Ellipt calls the device 'Kibo'.
Dom returns from LA, but when Fleur informs Serena and Ric of his childish behaviour the young doctor begins to question his role on the wards. However, whilst taking a Malick's fiancé back up to the wards from X-ray Dom finds himself trapped in the lift. He manages to perform life-saving surgery in the lift, saving the day. Mary-Claire and Harry spend New Year's Eve together.
Mo prepares for Celia's wedding day, but nothing can prepare her for the secrets that are about to be revealed. Guy is horrified when Lisa returns to Holby after falling from a bridge, and finally accepts his daughter's medical condition.
Jac considers the possibility of starting a new life with Emma in the USA. Sacha is knocked for six when his daughter, Rachel, is admitted with amphetamines in her blood. Mo completes her first solo Herzig operation successfully.
Fletch's ex-wife, Natalie and her friend are admitted after a drunken night out ends in disaster. However the day ends in tragedy as Natalie dies from a bleed to the brain. Rachel sits her physics A-level mock, but when she throws up Arthur conducts more tests - only to reveal she's pregnant.
Sacha has the rug pulled from under him when he discovers Mr Kerrigan is the father of Rachel's baby. As he makes a professional attempt to call the police, his plans are severed by Rachel's threat to cut him out of her life forever. Mary-Claire realises she's developed feelings for Harry. Adele learns her and Mo are not sisters.
Mary-Claire is promoted by Fletch for one day. She treats homeless man Pat, who later dies. When Harry states no one will miss Pat she questions their relationship status. A 19 year-old boy dies from a crash, so when a male is admitted requiring a heart and liver transplant the father agrees to use his stepson's organs, much to the disapproval of the mother.
Sacha suffers yet another crisis as daughter Rachel leaves the wards to meet up with Mr Kerrigan in the woods, however she collapses whilst riding her bike. She miscarries during surgery. Harry is upset after realising how strong his feelings are for Mary-Claire, but learns she's dating another man.
Sacha is understandably emotionally drained from the previous weeks of hassle, and when Mr Kerrigan arrives he punches him. Jonny starts a petition against Guy after schedule changes are made to the operating theatre, but he gets more than bargained for when a patient makes his campaign go viral. Mr Kerrigan hands himself in to the police.
Elliot is excited as the day arrives to officially test his Kibo device on a patient. However Julie Kale dies after the Kibo operation, causing Elliot to question himself. Jonny told Guy just hours before she died that a patient needed to die to make Guy realise the damage he's caused.
Harry finally tells Marie-Claire that he loves her and the disaster strikes as he goes to save a patient and in doing this he takes a tragic fall. The fall leaves him fighting for his life Meanwhile Johnny tries to come to terms with the loss of a patient. Guy tries to find a reason for this death. Zosia fears she is being sidelined so she takes matters into her own hands.
Jonny awakes from a nightmare in a prison cell, and befriends his terrified prison cell mate. However as Mo and Adele visit Jonny is involved in a fight and he and his cell mate are stabbed. Guy is furious that Jonny is back and demands to get him back in prison as soon as possible. Fletch's daughter Evie helps Harry stop pushing everyone he needs away.
Raf is horrified to learn his mother has died as the day of Harry's facial reconstruction arrives. Despite all the news Raf continues and his operation is a success. Arthur treats a mountain climber but is adamant he cut the rope of his friend trying to kill him. Serena is furious over his actions, reminding him he's a doctor, not a detective.
Adele is stunned to see Steve outside Holby, and invites him up to Darwin. Guy arrives on Darwin as well as a VIP arrives on the wards. When Steve forces his way into the VIP's room Guy is horrified and demands him to be removed. However, before Steve can be removed he reveals he changed the battery which landed Jonny in prison. He agrees to share his news with the Police. Harry has facial surgery, but demands more pushing away the people he loves most.
Jonny is released from prison but struggles with the betrayal of Guy. When former cell mate Archie is admitted because of an overdose it pushes Jonny over the edge, so he blames the people he loves. After an incredibly stressful day for both Jac and Jonny - they leave hand in hand for a new life. Sacha is stunned by Essie's return, especially when she's harbouring a secret.
Guy prepares himself for the launch of the Supercentre - but with Jac missing and his day crumbling the CEO makes a life-changing decision. Mary-Claire celebrates her last day, but Harry ruins it for her. They end up in the back of an ambulance and he proposes, but will Mary-Claire say yes?
Fletch is optimistic about Evie's first day at her new school, but his happiness is soon dashed when her school bus and a van crash. Evie claims she hit her head on the window, so Fletch calls on a CT, worried she may suffer what her mother did. Annabelle Cooper, a new neurosurgeon arrives on the wards and causes a stir.
Guy, Zosia and Annabelle treat a 21-year-old, but when they discover he has a brain tumour which will kill him in a year memories come flooding back for Guy and Zosia. Serena treats Anges when he dislocates his shoulder, and when he asks her on a date she accepts. A new CEO arrives - but it's a blast from the past when the face is revealed to be none other than Henrik Hanssen.
Henrik returns as CEO of Holby City, and without any hesitation assigns all doctors their roles for an influx of casualties after a May Day march turns into a riot. Furthermore, Henrik cuts Guy's funding for neurosurgery. Oliver Valentine returns, but Jesse isn't impressed by his attitude to patients. Zosia discovers Annabelle has a fatal brain tumour.
Zosia learns Annabelle's tumour has grown, exerting more pressure on Annabelle to find a life-saving cure. Raf shares his enthusiasm and inspiration of Hanssen to Serena, so she gives him a chance to impress him, however his plans are scuppered. Adele attempts to build bridges between Mo and her father.
Oliver makes a fatal mistake in theatre, forcing him to impress Jesse, Henrik and Elliot if he's to keep his place in Holby. Sacha asks Essie to meet his children, making Essie question the speed of their relationship, while Raf discovers Lucy is being abused.
Raf's patient, Lucy, returns for surgery, but Cara has her doubts about the procedure. Zosia irritates Ollie when she arrives late for her first shift on Darwin. Adele tells Jesse she has failed her nursing degree course.
Zosia and Ollie fear for a patient who has a heart condition but believes she has a fictional disease. They call upon psychiatrist Seb, who later asks Zosia out on a date. Guy works on a risky procedure, but defies Hanssen's orders and removes more of a tumour than he should.
A new F1 arrives on AAU, Morven, and she is instantly paired with Arthur on her first day, but when a patient dies during surgery, Arthur has a panic attack. Mr T and Clifford clash over Mo. Dom is left stunned when his mother arrives unexpectedly.
Fletch realises he's in too deep with the pharmaceutical robbery, and he cannot pull, what will he do? Essie messes up her interview for Transplant Coordinator, but an inspirational speech soon gets her the job.