Excerpt from the study guide:
Greville is also flexible. After he comes up with an explanation that appears to fit all the facts, he still questions it from time to time. For instance, after he realizes Marion took part in David Miller’s murder, he also comes up with alternative explanations of why she might have dropped the hair dryer in the bath. This shows that he admits the possibility that he can be wrong.
Greville has good knowledge of human behavior and motivation. He can predict how people behave in different situations, and what motivates them. He realizes why the children committed the murders and is also able to predict that they will commit more murders. He cab even guess their future targets.
Greville also knows how to get the desired reaction out of people. He successfully baits Payne to tell him what he thinks, despite Payne’s reluctance to do so. Having guessed that his superiors will not approve of his theory regarding the significance of Marion’s gesture, he hides it from them while applying for permission to see her. All these highlight that he is a good psychologist.
Greville’s intuition sometimes gets ahead of his logical reasoning. For instance, he gives “a small shudder for the new arrivals” at Pangbourne, without being able to explain why. This shows that he feels that something is wrong about the Pangbourne estate even before he solves the mystery using logic and physical evidence. His intuition tells him something about the estate is what led to the murders. This shows that he is perceptive. His experience and skills allow him to focus on the root of the problem immediately ...