Every day the girls face life, death and lunacy on the wards of St. Margaret's; every night they let off steam, with a dangerous appetite for uncomplicated sex and unruly misbehaviour.
Kate has started a new Nurse Practitioner course and is full of fresh ideas for the ward. So when a suspected case of anthrax walks through the door she takes charge and puts her staff in quarantine.
Beth is still convinced nurse Justyn tricked her about his sexuality just to get her into bed. So in true Beth fashion she plans revenge and plays a trick of her own.
Anji turns up to work an hour and a half late after a champagne breakfast, a patient susses that she has been drinking and Kate has no choice but to take disciplinary action against her friend. Then, to the surprise and horror of her three friends, Anji quits her job.
After quitting her job at the hospital, Anji has taken the plunge and decided to go travelling around India. Beth is anxious about what life will be like without her: she secretly worries that Anji is the only reason that Lia and Kate are friends with her. And then she catches the two of them having an impromptu drink in the pub without her...
Back on the ward, Dr Callum is jealous of nurse Justyn's popularity with the patients. When he discovers this is down to Justyn's 'professional campness', he persuades Justyn to teach him the basics.
A new addition to the ward, registrar and ex-army doctor Peter Compton, gets a welcome he won't forget when all the guests at a wedding reception turn up at MAU with a nasty case of food poisoning.
Dr McManus's reputation as a basket case and his increasingly strange behaviour worry Peter. Kate defends McManus and sets about trying to work out what's the cause of his erratic outbursts. In an attempt to build bridges with Peter, Kate finds herself on an unconventional Friday night "business meeting", but is his interest in her on more than just a professional level?
Lia is dismayed to discover that Jamie has been offered a job in Australia. Can he muster the courage to accept the job? Will she agree to go with him? Could she bear to leave her daughter behind?
Callum volunteers to take part in overnight clinical trials for a mystery drug. When Beth finds out how much money he is making, she and Justyn decide to join him. But they can't understand why they are suffering adverse symptoms while Callum is smugly acting as normal...
With her 30th birthday fast approaching, Kate worries that her age is starting to show in the most unusual of places. She is happy about her budding relationship with new registrar Dr Peter Compton, despite the ridicule she gets from Beth and Lia when they realise she and Peter haven't had sex yet.
The nurses at St Margaret's are feeling increasingly under threat from violent patents. Unimpressed with the new, prepubescent security guards, Peter uses his army training to give self-defence lessons to the rest of the staff.
Kate's mother, Valerie, surprises Kate with a special birthday visit. Unfortunately, Valerie is more interested in joining Lia and Beth on a boozy night out than spending quality time with her daughter. But Lia and Beth have a surprise - or two - in store for Kate.
Anji is home, is pregnant and has picked up a newfound spirituality on her travels so seems entirely unconcerned about the practicalities of having a baby on her own. Reality bites when she applies for her old job as an HCA. After trying to offer the baby to her sister, Anji comes up with a plan to find her best 'conquest' and tell him he's the dad.
Meanwhile, single parent Lia is asked by her daughter Emma to go to a craft evening with her. When the group leader points out that Lia and Emma have 'communication issues' Lia decides to take action.
Beth takes offence when Steph, the insecure girlfriend of a good-looking male patient, Patrick, has a go at her for flirting. Beth decides to teach her a lesson and while tending to Patrick's wound, deliberately glues herself to him. Stuck together for 24 hours, Beth uses the opportunity to wreak more havoc for jealous Steph. She tells Patrick there is nothing a woman likes more than total honesty, even when it comes to secret male fantasies. Little did she know that in this instance, honesty really is the best policy.
Anji is planning a camping trip with Rob - a plumber at the hospital - until Judith warns her of the dangers of going camping while pregnant. So Rob is left looking for a camping buddy and, much to everyone's surprise and amusement, Beth is cajoled into taking up the challenge.
Kate is thrown into a frenzy of confusion when Peter makes a comment that she thinks could be his version of a marriage proposal, but is then humiliated when he tells her his passing comment was not a proposal at all.
A series of further cryptic messages leads Kate to realise that Peter is asking her to go to a Garden Centre at 8pm. Suddenly fearing he is about to dump her, she turns up - only to find a candle-lit dinner laid on to the sound of a string quartet...
She's only just got engaged, but Kate is already driving her three friends mad with talk of dresses and flowers. Her fiancé Peter, however, doesn't think there's any need for such fuss.
Lia meets a younger man and starts to party like she's 18 again, until she has to give a lesson in sex education at her daughter Emma's school and discovers she knows more about teenagers than she first thought.
Meanwhile, Beth agrees to give hospital plumber Rob a second chance and goes on a date with him. And Anji is caught in an awkward situation when both Callum and Beth offer to be her birthing partner.
As her wedding to Peter approaches, Kate takes him to visit what could be their dream home in the country, but he doesn't seem overly impressed.
Anji proudly shows off her new baby, but still hasn't made up with Callum, who is avoiding her in the hospital.
Beth and Rob are getting on brilliantly and already seem like they've been a couple for ages.
Meanwhile, unhappy Lia sees everyone else around her moving on. Emma can tell her mum hasn't been happy since Jamie left and tries to convince her that a trip to Australia may be just the tonic