"Evolve or Be Extinct" is the 829th episode of Casualty and the 6th episode of the 27th series. It was preceded by "I'll See You in My Dreams" and followed by "Tough Love". The episode was directed by Jon Sen and written by Andy Rattenbury.
Ryan Bradshaw heads out to meet his girlfriend's daughter for the first time, and gets the shock of his life as an old acquaintance, Connor, turns up at the same restaurant. Connor makes a run for it, quickly ending up in the ED, but what spooked him and how is he linked to Ryan? Meanwhile, hung-over medical student Annie arrives at Holby having broken her arm following a night out, and Lloyd also spends the day feeling a little worse for wear after letting his hair down with Fletch.