Gets characterisation of the Doctor and Martha wrong, they feel off, and less endearing and this makes the story harder to invest in. Besides this, a great horror story - using a lot of horror elements well, in a really well paced story, with some likeable and strong side characters, in an eerie, well developed setting. Minor tweaks to the Doctor and Martha's dialogue to better characterise them how we know them, would really have elevated this into great territory.