Gina puts Connie in a difficult position when she asks her for help behind Elliot's back. Connie must then decide where her loyalties lie. Ric's skills are tested when he has to operate on an obese woman. Matt and Reg find more evidence of drug tampering.

Michael faces his appeal hearing, and uses the opportunity to try to patch things up with Connie, while Sam shares a secret with Chrissie. Lola discovers Leanne's father Steve has been admitted, and becomes convinced he is a drug user.

Connie's heart battles her mind as she wonders if she should stay at Holby. Mark learns to respect the way Tricia wants to handle her cancer.

Elliot lets his personal feelings get the better of him when Gina is re-admitted. Sam is put on report but continues to do things on his own terms - will he learn his lesson?

Abra supervises Diane as he covers for Ric for a fortnight, and reveals he would be keen to work at the hospital permanently - but his determination to perform an operation tempts him to bend the rules, and ruins his chances. Tricia tells Chrissie about her relationship with Mark, and decides to have her surgery moved forward.

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.

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.

Jordan helps Connie save the day when a black tie charity dinner turns into a disaster zone. In an attempt to ingratiate himself with Kyla, Justin offers to look after Max.

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.

Elliot fears for his wife, who has motor neurone disease and whose health appears to be getting worse. He also regrets their decision to keep her condition a secret from Martha - not realising she knows something is up and has persuaded Joseph to help her learn the truth. Sam uncovers a family secret when he treats a boy with two mothers who is undergoing a heart transplant.

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.

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.

Chrissie panics when Don Bosman returns to the hospital to get Helena's body and finds out her heart was donated without his consent. Dillon's condition worsens after being readmitted, leading Sam to discover he has failed to conquer his drinking habit. Meanwhile, jealousy gets the better of Kyla, who berates Justin for behaving unprofessionally after catching him flirting with Donna.

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.

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.

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.

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.

Diane is told to work under Ric's supervision when she is blamed for Helen's death, but she is determined to clear her name and attempts to secretly record Nick confessing to his error. A new assistant general manager starts work at the hospital, and soon invites Donna to the May ball, while Matt gets a second job in the admin department to pay off his debts.

Nic Jordan steps up his campaign to get back into CT. Mark tries to save Chrissie from a painful truth, but unearths shocking news about Tricia.

Lola makes a drastic decision regarding baby Leeanne's care. Reg wonders if Bradley's intentions towards Donna are honourable. Jac works closely with Joseph.

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.

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

Matt and Donna row over Bridie's death, with both keen to blame the other, but the arrival of the nurse's grandmother visiting her boyfriend in the hospital gives the doctor a chance to offer an olive branch. Connie offers Sam a position as trainee rep as the pair grow closer, much to Chrissie's annoyance, and a patient's dad asks Lola out on a date.

The hospital staff have their work cut out after a car pile-up, giving Kyla the chance to earn some extra money to put toward her legal fight to keep Max. After their night of passion, Connie and Sam flirt with each other despite professional disagreements as they treat an injured couple, and Mark prepares to pop the question to Tricia.