The direct object is what accompanies the verb and which tells us to whom the action is directed.
The direct object pronoun is used to replace the person or thing that is performing the action of a verb, and is used so that the sentence is not so repetitive and more pleasing to the eye.
Since Mrs. Dombey reacts with surprise to her husband simply calling her "my dear," we can infer that Mr. Dombey is usually formal and distant to his wife.
