But he gave no clue as to the line on which he proposed to operate. Only over and over again he gave utterance to one phrase. “It is the greatest mistake to underestimate your adversary. Remember that, mon ami .” And I realized that that was the pitfall he was striving at all costs to avoid.

So matters went on until the end of March, and then one morning Poirot made a remark which startled me considerably.

“This morning, my friend, I should recommend the best suit. We go to call upon the Home Secretary.”

“Indeed? That is very exciting. He has called you in to take up a case?”