Casualty will mark its 30th anniversary with a feature-length episode that will include "a shocking stunt", the show's producer has said.
Too Old For This Shift, the milestone instalment about Holby City Hospital's emergency department (ED), will be broadcast on August 27.
It will include scenes that will hit "the very heart of the hospital" as key characters will be put in peril.
Fans are promised a trip down memory lane as some much-loved faces from the show's past return.
Stalwart Charlie Fairhead, played by Derek Thompson, will also be celebrated as he reaches 30 years of service to the NHS. But the beating heart of Holby's ED will not have a smooth ride in the special episode. The team will have to support Charlie and the ED staff in this moment of turmoil.
Belfast-born Charlie has been a Casualty cast member since its debut on BBC One.
He said: "From day one of filming Casualty in 1986, I've been so proud of its true to life storytelling, representing everything the NHS stands for."
The 68-year-old added: "I've been a part of a few anniversaries over the years, but this really feels like a significant moment in British television history."
The heart-wrenching extended Casualty storyline will also see a crossover with sister show Holby City. Holby's cardiothoracic consultant Jac Naylor (Rosie Marcel), chief executive Henrik Hanssen (Guy Henry) and Adrian "Fletch" Fletcher (Alex Walkinshaw) will play key parts in Too Old For This Shift.
Executive producer Oliver Kent said: "Casualty's 30th anniversary episode is a huge celebration of everything that the show does best." He also said the feature-length action film "will make the audience gasp, laugh and cry buckets".
He added: "There will be plenty of surprises for the audience, including some old faces that they won't have seen for a while. Best of all, it has the incredible Charlie Fairhead centre stage."
Casualty is the longest-running emergency medical drama series in the world. It has endured due to a combination of powerful acting and writing.
Casualty currently averages 5.35 million viewers when consolidated figures - the audience watching on catch-up services - are added to the numbers who watch live.
The 1,000th episode was broadcast on June 25 and saw the return of original cast member Cathy Shipton as Lisa "Duffy" Duffin.