Clara has it all under control: her life at school, her life in space; her new boyfriend and her mad old Time Lord. Everything is humming along just fine, so long as everybody never actually meets. And then, one morning, just before assembly, Coal Hill welcomes a new relief caretaker with a Scottish accent.

In the mysterious world of the Nethersphere, plans have been drawn. Old friends and old enemies manoeuvre around The Doctor, and an impossible choice is looming over him.

With Cybermen on the streets of London, old friends unite against old enemies and the Doctor takes to the air in a startling new role. As the Doctor faces his greatest challenge, sacrifices must be made before the day is won.