Heaven Sent

As if the death of his best friend wasn't enough, the Doctor's situation has only gotten worse. What initially started as an attempt to help clear someone of a false murder charge has evolved into to something much worse.

Now trapped in an old rusty castle in the middle of an ocean, the Time Lord is being stalked by a mysterious creature that only pauses when he gives up his deepest secrets. What does this thing want? And can the Doctor escape and find his way back home?