"And Then There Were Three" is the 689th episode of Casualty and the 3rd episode of the 24th series. It was preceded by "Dawn of the ED - Part Two" and followed by "Sunset Syndrome". The episode was directed by Ian Barnes and written by Mark Catley.
It's the F2s first shift after Heather's death. All three are nervous, and their confidence sinks further when Adam palms them off onto Zoe for the day - he's got too much to deal with in the wake of Heather's accident.
Zoe, equally stressed over her 'mother's' illness, divides the trio - Yuki is sent on a shout with Jeff and Polly and Lenny and May are assigned mentors for the day: Lenny with Zoe and May with Ruth. All three struggle in their own way and are banned from treating patients for the rest of the shift.
Later, in a counselling session with Ben, the trio struggle to open up. But, eventually, each in turn reveal that Heather's death has shaken them. Ben identifies that each of them are missing a part of themselves: just like the Wizard of Oz, May needs a brain, Lenny a heart and Yuki some courage. The three resolve to work on their flaws and realise they can help each other by working as a team.
As the new team celebrates in the pub later that evening, Zoe slips out to make a call on her mobile...