Charlie, Mary Boyle’s fiancé, is obviously from a different class than the residents of the tenement.
He is a professional man who was a teacher, but who is now training to be a lawyer.
It is from Charlie that the family receive the news they’ll inherit money from a relative.
He does not seem to be very competent despite his education.
It is implied that it is because of this incompetence that the inheritance will not come to the Boyle family.
He manipulates the Boyles. He compliments Mary and behaves courteously towards Mrs Boyle, telling her “Please don’t put yourself to any trouble."
We find out that he is not what he seems. It is his abandonment of Mary - without any explanation - which makes him a "scoundrel".
Although it is never made clear whether he knew she was pregnant, Mary is left single and with no financial support for her baby.
Bentham seems happy to marry into the Boyle family when it appears there is money, but he vanishes as soon as he learns the inheritance will not be forthcoming.