In this he was faced with an unpleasant situation.

He cared nothing about Mallalieu.

If Mallalieu was a guilty man, let Mallalieu pay the richly-deserved consequences of his misdeeds.
Brereton, without being indifferent or vindictive or callous, knew that it would not give him one extra heart-throb if he heard Mallalieu found guilty and sentenced to the gallows.

But Cotherstone was the father of the girl to whom Windle Bent was shortly to be married--and Bent and Brereton had been close friends ever since they first went to school together.
It was a sad situation, an unpleasant thing to face.

He had come on a visit to Bent, he had prolonged that visit in order to defend a man whom he firmly believed to be as innocent as a child--and now he was to bring disgrace and shame on a family with whom his host and friend was soon to be allied by the closest of ties.