"In my opinion it is of very considerable importance. Miss Monkton," he replied. "I think it will help us." "It certainly proves that he had a secret enemy," interjected Wingate, "and one who would hesitate at nothing that would secure him revenge." "I quite agree, sir. The letter breathes the most intense hatred in every line. The motive of that hatred we have got to discover." Then the detective, turning to Sheila, said: "Now, Miss Monkton, there is a little information that I am sure you will be able to give us. I am not so well posted in your father's biography as I ought to be. But, before he became a prominent politician, I understand that he was a barrister with an extensive and lucrative practice." "That is so," corroborated Sheila. "He did not often talk about those times, but I have always understood that he made quite a big income at the Bar." "And when did he retire from his profession?" "About fifteen years ago." "And he resolved to say good-bye to the Bar and devote himself entirely to politics?" Sheila nodded. "That is quite true. He had a very firm opinion that a man could not serve two masters." "Was he on the Chancery or the Common Law side?" was Smeaton's next question. "On the Common Law," replied Sheila. "But why do you ask that question?" "You shall know in good time. Miss Monkton. Well, we may take it, then, that this vindictive letter was written more than fifteen years ago." "While he was still at the Bar," interrupted Wingate, who was beginning to realise the point of the detective's reasoning. "You are assuming that this venomous epistle did not come from a political enemy." "It is an assumption for which I have reasonable grounds," was Smeaton's answer. "There has been no bitterness in party politics ever since Mr Monkton became a conspicuous figure in the House. And we know that, while he was most popular with his own side, he was respected and liked by his political opponents." "Is it too much to ask you to give us the benefit of any theory you have formed, Mr Smeaton?" suggested Sheila, in her pretty, gracious way. "With all the pleasure in life, my dear young lady. This letter goes back, in my opinion, to your father's barrister days, when he was one of the foremost counsel in England. I asked you just now whether he was on the Equity or the Common Law side, and you wondered why I asked the question." "I am still wondering," said Sheila simply. "On the Equity side they try all sorts of cases concerned with points of law, the majority of them of a very dry and uninteresting character. I should not look in an Equity case for a defeated litigant who would turn into a vindictive enemy of the type of the writer of this letter." The young people began to see, as yet very dimly, whither he was leading them.