Just about the time that he made this resolve, Robin in his rooms in the Temple was hanging up the receiver of his telephone with a dazed expression in his eyes. Mr. Manderton had rung him up with a piece of intelligence which fairly bewildered him. It bewildered Mr. Manderton also, as the detective was frank enough to acknowledge. Mary Trevert had gone to Rotterdam for a few days in company with her cousin, Major Euan MacTavish. Mr. Manderton had received this astonishing information by telephone from Harkings a few minutes before. “It bothers me properly, Mr. Greve, sir,” the detective had added. “There’s only one thing for it, Manderton,” Robin had said; “I’ll have to go after her ...” “The very thing I was about to suggest myself, Mr. Greve. You’re unofficial-like and can be more helpful than if we detailed one of our own people from the Yard. And with the investigation in its present stage I don’t reely feel justified in going off on a wild-goose chase myself. There are several important enquiries going forward now, notably as to where Mr. Parrish bought his pistol. But we certainly ought to find out what takes Miss Trevert careering off to Rotterdam in this way ...” “It seems almost incredible,” Robin had said, “but it looks to me as though Miss Trevert must have found out something about the letter ...” “Or found it herself ...” “By Jove! She was in the library when Bruce Wright was there. This settles it, Manderton. I must go!” “Then,” said the detective, “I’m going to entrust you with that slotted sheet of paper again. For I have an idea, Mr. Greve, that you may get a glimpse of that letter before I do. I’ll send a messenger round with it at once.” Then a difficulty arose. Manderton had not got the girl’s address. They had no address at Harkings. Nor did he know what train Miss Trevert had taken. She might have gone by the 9 P.M. that night. Had Mr. Greve got a passport? Yes, Robin had a passport, but it was not viséed for Holland. That meant he could not leave until the following evening. Then Robin had a “brain wave.” “There’s an air service to Rotterdam!” he exclaimed. “It doesn’t leave till noon. A pal of mine went across by it only last week. That will leave me time to get my passport stamped at the Dutch Consulate, to catch the air mail, and be in Rotterdam by tea-time! And, Manderton, I shall go to the Grand Hotel. That’s where my friend stopped. Wire me there if there’s any news ...”