" the “power of three”?’ she asked. She cast her eyes around the room and everybody stared back, but nobody spoke. ‘It’s a concept that some people believe in: that the number three stands for that which is solid, real, substantial, complete – for example the three dimensions of length, breadth and height which are necessary to form a solid. There are three great divisions that complete time: the past, the present and the future. Thought, word and deed complete the sum of human capability; animal, vegetable, mineral – the three kingdoms of the natural world. I could go on. For some people, three is such a powerful number that everything has to be finished in threes for them to feel safe. A famous physicist, Nicola Tesla, was so obsessed with the number that he used to walk round the block three times before he would enter a building.’ She paused and again looked around the room, taking them all in, but her gaze settled on Tom, who instantly felt guilty about his scepticism. ‘If this is his driver, he will try to kill one more girl to replace the failed attempt. She will look like the other three, but this time he will be sure to finish the job. I’m using “he” throughout this presentation because, as we know, the chances are that the killer is a man. However, “he” could just as easily be more than one man.’ She paused and every eye was on her. ‘But there’s another theory that fits the profile. I would like to suggest to you that there was only one victim that mattered to the killer. Only one person who had to die. The others were decoys, added to confuse us. Three may have been chosen as the best number to ensure the police were chasing their tails trying to find a link between the victims when there isn’t one. And "
― Rachel Abbott , Kill Me Again (DCI Tom Douglas, #5)