Other mistake: When the old well needs filling in, for safety reasons, Ryan is breaking up bricks. If you are filling up a well, first, you'd need lots of bricks and stones, heaps more than Ryan's small pile, and, two, why does Ryan have to break up the bricks? They're going into the well - it doesn't matter if they are big or small.
Continuity mistake: Near the end, Rosemary has a photo in her right hand. When Dr Fairborne starts to get aggressive, at first, Rosemary tries to keep the photo away from him, but when he grabs her and threatens her with a scythe on her neck, the photo has vanished.
Revealing mistake: After the Custos's house has been broken into, the next day, the Custos takes a key out of his jacket pocket, unlocks a drawer and takes out a pile of bound papers. When he closes the drawer, he doesn't take the key out of the lock, but he pantomimes his hand returning the key to his pocket.
Character mistake: When Angus is found dead, he left a word, "murder", in steam on the mirror. Daisy cleaned off the word before anybody, except Laura, could see it. Later, Daisy said that Laura was annoyed with her because she had wiped the words, plural, off the mirror. But it was only one word.
Continuity mistake: While the girls are packing up Charlie's belongings after he died, Rosemary brings out the small bag from the bathroom. Laura is seen rummaging around in the bag, looking for Charlie's auto-injector, but she just moves them around, until the next shot, where she suddenly has half of the items out of the bag and in her hand.
Continuity mistake: When the police are interviewing people about Mr Volker's death, the girls are talking to the lawnmower man, who turns the ignition on and releases the brake, but in the next shot he reaches down to release the brake, despite having already done it.