Continuity mistake: While Emma is explaining to Clara what an empathic psychic is, the Doctor grabs a bottle of milk from the table and takes a swig out of it, holding the bottle in his right hand, before jumping into the conversation to state that empaths are both extremely compassionate and extremely lonely. While he's saying this, his left hand goes from gesturing in a close-up to holding the milk bottle in a wide shot. (00:06:25)skater49th
Continuity mistake: When Clara draws the Doctor's attention to the vision of a forest appearing in the archway, the candelabra she is holding has two candles in it, with the third hole empty. Moments later, after the apparition has disappeared, there are now three candles in it. (00:15:30)
Continuity mistake: For most of the episode, there is a thunderstorm going on at Caliburn House. However, when the TARDIS is seen dematerializing and rematerializing when the Doctor and Clara go to take pictures of the ghost throughout time, it's dry in the grove where it was parked. The first time is especially noticeable, as moments later we are shown Professor Palmer and Emma looking through a rain-spattered window, commenting on the noise of the TARDIS' engines.