The TARDIS strands Eleven at Clara's — six years later than he meant to arrive. Trapped across his timeline and up to his delicate eyebrows in spoilers, he receives a cryptic message from Twelve: one of his former companions is in danger, and he'll need the help of the others to save her. It's a reunion the Doctor would love to remember... but the laws of time doom him to forget.

When the echoes of a million lifetimes threaten to tear Clara's mind apart, she's rescued by the last savior she'd ever expect: that 'grumpy old cow', the TARDIS. Unfortunately for Clara, sanity comes at a rather steep price: periodic possession by a certain bitey mad lady who's growing ever-fonder of being human. 11/Clara, 11/Idris.