Two patients await life-saving surgery at St Mary's in Paddington, the biggest of five hospitals in the Trust. They both need a bed on the intensive care ward. But the hospital is full to capacity and there is only one bed left.

While the hospital tries to discharge patients, new ones continue to arrive. Peter Lai, a 60 year old retired software engineer arrives at the hospital for a lifesaving operation on an aortic aneurysm in his chest.

After collapsing at work, 48-year-old crane driver Phil is becoming increasingly paralysed with each passing day. Kevin O'Neill, one of the country's leading brain surgeons, diagnoses him with a fast-growing brain tumour and decides to perform a potentially life-threatening operation to remove it. But as the clock ticks, securing theatre time for Phil is not straightforward in a hospital approaching full capacity. O'Neill and his colleagues deal with some of the country's most complex and challenging neurological cases. Their work is so in demand, the department has one of the longest waiting lists in the country. But the hospital is determined to clear the backlog of patients - some have been waiting for their operations for over a year. The pressure is on for O'Neill and his team to get through a packed list. At the same time, the Trust is pioneering a form of non-invasive brain surgery that replaces knives and drills with MRI-focused ultrasound waves. Consultant neurologist Dr Peter Bain says: "The first time I saw an operation like this was on Star Trek". One of his first patients is Selwyn, a 52-year-old painter and decorator with an uncontrollable tremor. If successful, Selwyn's operation could pave the way for significant reductions in brain surgery recovery times and potentially reduce patient waiting times for some brain surgeries.

A woman from Nigeria recovers in the hospital after going into premature labour with quadruplets having fallen ill on a flight. She receives a visit from the hospital's overseas officer Terry, whose job it is to prepare her for a huge bill. Because she is not a British resident, she must pay for the care that she and her babies are receiving. The cost of such specialist care quickly tops £100,000 and looks likely to rise to half a million pounds during their stay. Terry explains that, despite her distressing predicament, it is a legal requirement for the hospital to collect the money the NHS is owed. The woman is just one of a number of overseas patients who are receiving lifesaving care and from whom the hospital must now try to recoup money. Although emergency treatment given in A&E is free, non-UK residents who are admitted to a ward have to be billed.

This episode looks at pioneering treatments for some of the oldest and youngest patients in the hospital. A 98-year-old man arrives at Hammersmith Hospital for a landmark heart operation. The operation known as TAVI is offered to patients who are deemed not suitable for open heart surgery. Without the op, John has been told he has only a 50 percent chance of surviving the next six months. The clock is also ticking for 18-year-old Debbie at St Mary's Hospital, home to the Trust's specialist paediatric centre. Debbie is about to have a lifesaving bone marrow transplant which could cure her of sickle cell disease.

In the final episode of the series, surgeons are forced to use unconventional methods to get their operations completed against the odds. At Hammersmith Hospital, 31-year-old Jennifer is taking part in a groundbreaking scheme, as she donates her own kidney to save her husband Elliot's life. Meanwhile at St Mary's, 84-year-old Betty arrives to have her bowel cancer removed, but colorectal surgeon George Reese has to decide whether it is safe to go ahead with her operation as there are no beds available for her to recover in. Last in the series.