The episode, the first to be shot in HD, sees the unveiling of the new Emergency Department following the recent fire.
Jordan (Michael French) and Charlie (Derek Thompson) decide that the department will only treat minor cases on the team’s first day back.
But they’re forced to change their plans when a huge traffic accident occurs on the dual carriageway, a cloud of poisonous gas engulfs the town and victims start to flood into Holby City.
The team are soon stretched, despite the arrival of dashing new doctor Tom (Oliver Coleman) who arrives by air ambulance.
How will the staff cope with one of their most challenging days to date…?
Saturday 7th January, 8.40-10.00pm on BBC One and BBC One HD