For the life of him he could not classify Robert Hume-Frazer.

The man was either a consummate scoundrel, the cold-blooded murderer of Margaret's brother, or a maligned and ill-used man.
Within a few minutes he would be called upon to treat him in one category or the other.

A few questions might elucidate matters considerably.
The hiatus in the conversation created by the mention of Capella gave him an opportunity.
"Did you endeavour to raise the requisite capital for your estate in London only ?" he inquired.
"No; I tried elsewhere," was the quick rejoinder.
"Here, for instance, on the New Year's Eve before last ?" "Now, how the blazes did you learn that ?" came the fierce demand, the speaker's excitement rendering him careless of the words he used.
"It is true, then ?" "Yes, but--" "Robert!--" Margaret's voice was choking, and her face was woefully white once more--"were you--here--when Alan--was killed ?" "No, not exactly.

This thing bewilders me.

Let me explain.