Montague Small (Monty), the Gavender's neighbor, is a rich and successful writer. His wife Sophie died of cancer and though he knows she didn't really love him it is a difficult loss to bear. Leonie, his mother, never liked Sophie and felt happy the day she died. Now she wants to move in with him. Monty knows all about Blaise's extra-marital affairs (see Magnus Bowles), which has caused him to feel sympathy for the latter's wife. May this feeling develop into something else?
When Harriet received Blaise's first letter, in which he confessed his infidelity, she behaved in a remarkable way. She took hold of the situation, forgave Blaise, and even decided to meet Emily. Monty really admired her at this point in the story.
But Harriet, after the second letter, breaks down completely, almost to the point of going mad. She moves in with Monty, who already had to deal with Edgar staying there, and becomes an incredible burden for him. She throws herself at him, telling him she loves him and wanting him to love her. What had once been a feeling of admiration, now turned into desdain, and he refuses her. He now sees her as an invader, an usurper of his privacy, and wishes she would leave. Instead, he decides he will leave.
Monty had a terrible secret. His wife Sophie was supposed to have died of cancer, but she didn't: he killed her. She was going to die anyway, but he could not stand her anymore. She was afraid of dying, and became very bitter to him. She screamed at him all the time, told him she didn't love him, that she had had many lovers (all better than him)... She hurt him so much that one day he strangled her to death. Nobody knew this secret, except Edgar.