Some info from another forum;
Flybe DH8 G-PRPB operating flight BE1331 EDI-LCY returned this morning and was evacuated on the runway.
I had a look at the flight replay on FR24. It departed 76 minutes late at 08:16 and climbed normally to FL170 then squawked 7700 near Talla and returned. Climb rate and speed looked normal until it levelled out and decelerated near Talla. Descent rate looked normal. It took a slightly longer approach route over Aberlady and slightly longer final approach, presumably to help it to lose height, but not unusually long. Descent and approach speeds looked reasonably normal too. It landed back in EDI at around 08:40 and the runway reopened about 30 minutes later.
According to FR24 (admittedly, not a perfect source of data), the aircraft involved in the incident is still at EDI. I don't know the nature of the emergency.