Patrick Maloney is a pretty despicable husband, as evidenced by the details below:
He is a man who needs to be taken care of. In itself, this isn't the most horrendous detail of his character. But within the context of his deception, it is notable. When he gets home, he awaits his wife as she prepares his drink. He allows her to collect his coat. Mary quietly waits for him to acknowledge her, as "she knew he didn't want to speak much until the first drink was finished." He has established himself as the dominating presence in this household, and his wife is expected to cater to his needs.
He's a good liar. Mary did not see this conversation coming. Her stunned response captures the way her husband has been deceiving her for quite some time:
Her first instinct was not to believe any of it. She thought that perhaps she'd imagined the whole thing. Perhaps, if she acted as though she had not heard him, she would find out that none of it had ever happened.
We can assume (based on his wording) that Patrick has been involved in an affair for long enough that he's developed a bond strong enough to leave his wife, yet he carefully hid all the details from her, leaving her in shock when he finally tells her the truth.
He's a hypocrite. Patrick is a policeman, sworn to serve and protect citizens from harm. Yet in his own home, he is unfaithful to his wife and decides to leave her when she's six months pregnant. And to add insult to injury, he asks Mary not to make any "trouble," because "It wouldn't be very good for [his] job."
Patrick's character is inexcusable, especially considering his wife's adoration of him.