Doctor Who: 10 Dropped Plot Threads We'll Never Get The Answer To

10. What Happened To Those Dalek/Time Lord Hybrids?

2015's season 9 opened with a bang with thrilling two-parter 'The Magician's Apprentice/The Witch's Familiar.' It featured the return of Missy, Skaro and Davros himself - exploring his childhood and adding new layers to the Dalek-creating tyrant.

The climax still left us scratching our heads, however. It's ultimately revealed that Davros' dying act was a ruse to get the Doctor to share some regeneration energy with him. The evil scientist siphons this off to his babies and so creates Dalek/Time Lord hybrids: basically Daleks with the power to regenerate.

There's a fatal flaw, though, as Davros' scheme also awoke the abandoned Dalek mutants in Skaro's sewers who rose up and attacked those with shells. The Doctor seems to treat this as the end of it but he couldn't have been paying close enough attention.

In shots of the exterior of the city, we can clearly see many Daleks patrolling the skies. Surely these weren't affected by the sewer mutants on the ground, which means they must still be out there somewhere.