Аннотация от автора:

From the Doctor Who Series Nine episodes "Under the Lake" and "Before the Flood." In an underwater base in Scotland, 2119 AD, a research crew find themselves under attack by fearsome alien ghosts. Cass (Sophie Stone), first name Jennifer, which wasn't revealed in the episode, takes charge after the commanding officer is killed, and aides the Doctor and Clara in defeating the ghosts. 

Cass, and her actress Sophie Stone, are both deaf and can only communicate through sign language, interpreted by her close friend Tim Lunn (Zaqi Ismail), but she is able to lipread, which comes in handy defeating the silent, chanting ghosts. 

I thought series nine was great, feeling though I was a little iffy, I can't quite explain it, but "Under the Lake/Before the Flood" were my favourites of the series, with Cass being my favourite supporting/guest character. And Sophie Stone was great too, her acting was brill.