I really liked the episode up until the end. It had a lot of promise, but it fell flat when Clara had her monologue at the end. So the whole thing was in the Doctor's head, and there aren't actually any monsters that are hiding? So what wrote on the chalkboard, and what was under the red blanket?
Why was the Doctor so sure that whatever was under the blanket wanted to be left alone? Maybe it was trying to meet them, but it left because it was upset that all the people in the room turned their backs on it.
And what was knocking on Clara's grandson's ship?
Why was Clara able to travel to Gallifrey? Isn't the planet trapped in time in some pocket dimension? If it could be time-travelled to, wouldn't the Doctor have done that by now?
The whole thing had such potential. It's a shame that the end ruined the rest of the episode for me.
