Chrissie visits Owen after taking a pregnancy test, fearing she may never be able to have children. Dean learns a lesson whilst shadowing Diane.

Parts three and four of a two-hour "Casualty@Holby City" special aired in four parts over consecutive weeknights. For parts one and two, see Casualty S20E09.

Lola discovers there is nothing wrong with asking for help. Mickie battles against rules and regulations only to find out that they are put there for a reason. Dean relises he can't put his personal pride before a patient.

With her eye on the Clinical Lead job, the arrival of new consultant Elliot Hope turns Connie's world upside down. Lola struggles when her daughter decides to move in with her boyfriend.

Mark is forced to leave the comfort of Darwin for the chaos of AAU. Elliot crosses Connie again and Donna oversteps the mark with disastrous results.

Ric performs extreme surgery on one of his patients, with disastrous consequences. Owen finally decides between Chrissie and Diane, and Matt bumps into a face from the past.

Diane passes her consultant's exam, but is she ready for promotion? Connie learns that Elliot can be a pillar of support. Meanwhile, Dean's future hangs in the balance.

Lola finds Amy drinking heavily in an attempt to cause a miscarriage. Donna decides to contact social services, but the troubled teenager's stepfather has other ideas and secretly arranges for her to go to another hospital. Chrissie tells Owen she is leaving Holby, forcing him to finally make a choice between her and Diane.

Abra returns to Holby with his nephew, who needs an urgent transplant. Ric is unable to operate because of the injury to his hand - but he relents when the patient's mother reveals a secret. Owen fears that he might get sacked for hitting Amy's stepfather, and that this could jeopardise his access to Katie. Diane tries to keep Laura from turning on her ex, but when she learns about his clandestine relationship with Chrissie, tragedy strikes.

Owen brings Katie to work to see the counsellor, as he is worried she is becoming too withdrawn. He also makes plans to spend Christmas with Chrissie, but when he overhears his daughter talking to Diane, he realises he must be clear about where his priorities lie. Amy is brought in for treatment following her miscarriage, and Nigel announces his intention to take legal action. However, Roz is beginning to suspect the truth about her husband.

Part two of a Casualty@Holby City crossover. For part one, see Casualty S20E17.

Two medics apply for the registrar's position, and Connie sees an opportunity to advance her own career when she learns one of the candidates has a very influential father (guest star Ronald Pickup). Mickie is offered a job as a nurse, but her mother urges her not to take it. Mark and Tricia reminisce about old times while treating a patient - but when it emerges that the woman was raped, bad memories come flooding back.

Ric has plenty of problems on his hands as the new ward opens - the thermostat breaks down and he is forced to take charge of an operation personally. Diane and Chrissie get into a heated argument over Owen in front of a patient, while Donna applies for a new job. However, she is surprised to learn Mickie has already been appointed, and wonders why she didn't say anything.

Frank's life insurance company asks for his medical records, and Tricia is afraid Mark will find out her secret. Despite her best efforts to cover things up, she is ultimately forced to confess that Chrissie is not his daughter. Jac returns to the hospital and Ric advises Diane that she should take some time off to deal with her personal problems - though she's adamant that it isn't necessary.

Jess returns to work after the death of her son but finds her newfound determination put to the test when young patient Archie presents with a lacerated spleen and she suspects possible child abuse. Meanwhile, Mark tries to deal with the news that Chrissie is not his daughter.

Connie's old school boyfriend Peter Holland arrives in the emergency department with a case of rheumatic fever and reveals childhood secrets about Connie. Mark and Lola become very involved in the treatment of two young brothers who have been beaten up. Elsewhere, Mickie loses her drunk patient Liz.

New nurse Kyla abandons a patient during a critical period and the rest of the team want answers. Meanwhile, in a bid to get Ric's support Jac and Diane go head to head in their procedures.

Sam performs a risky operation that he has never done before - to Connie's outrage. Elliot gets a new PA, but finds she cramps his style, while Chrissie receives a variety of Valentine's gifts from a secret admirer. Paul Nicholas guest stars as a patient whose vasectomy reversal goes horribly wrong.

Jac's determination to have Ric choose her as the new consultant has tragic consequences. Sam bends the rules again and is brought down to earth with a bump. A determined Lola fights to keep Princess at home.

A woman comes in for a heart transplant, and Connie persuades her to accept an experimental procedure that has never been tried before. Ric leaves Nick in charge while he is at the university, but Jac does not approve of his handling of a cancer patient's treatment and a past conflict between them resurfaces.

Mark gets over involved in a case which causes disastrous consequences. Meanwhile, Nick Jordan rocks Diane's world which may affect her relationship with Ric.

When Nick learns that Ric is away from Holby for the day he is determined to get one over on him. Meanwhile, Kyla learns that the best way to be a leader is to be herself.

Matt's parents want him discharged from hospital to be treated at home, while Mark blames himself for the stabbing. Donna flirts with a handsome physiotherapist, though Kyla warns her to stay away from him. The treatment of a heart patient causes conflict, as Connie wants to try the manufactured pump she helped develop, but Elliot is adamant a transplant is required.

Nick performs an unnecessary operation in his campaign for a transfer. However, when the patient's condition worsens, Jac is forced to take matters into her own hands. Matt and Dean undergo a student assessment with Lord Byrne, but may not be up to the challenge. Mark is plagued by his secrets as he treats a woman with problems similar to his own.

Connie is devastated when her patient collapses and there's not enough time to arrange a heart transplant. Nick tries to get Diane on his side by letting her perform a difficult procedure for the first time, while Ric talks her into taking the research position full time. Kyla brings Max to work as he is a diabetic and she is worried about his blood sugar levels.