“The grill,” remarked the big man authoritatively, “is one of the oldest dodges known to the Secret Service. It renders a conventional code absolutely undecipherable as long as it is skilfully worded, as it is in this case. You send your conventional code by one route, your key by another. I make no doubt that this was the way in which van der Spyck & Co. transacted their business with Hartley Parrish. They simply posted their conventional code letters through the post in the ordinary way, confident that there was nothing in them to catch the eye of the Censor’s Department. The key might be sent in half a dozen different ways, by hand, concealed in a newspaper, in a parcel ...” “So this,” said Robin, pointing at the letter, “was what caused Hartley Parrish to make his will. It would lead one to suppose that it was what induced him to commit suicide were not the presumption so strong that he was murdered. But who killed him? Was it Jeekes or Marbran?” Herr Schulz pitched his cigar-stump into an ash-tray. “That,” he said, “is the question which I am going to ask you gentlemen to help me answer. You will realize that legally we have not a leg to stand on. We are in a foreign country where, without first getting a warrant from London, we can take no steps whatever to run these fellows in. To get the Dutch police to move against these gentry in the matter of the assault upon Miss Trevert would waste valuable time. And we have to move quickly—before these two lads can get away. I therefore propose that we start this instant for the Villa Bergendal and try, if we are not too late, to force Marbran or Jeekes or both of them to a confession. That done, we can hold them if possible until we can get the Dutch police to apprehend them at the instance of Miss Trevert. Then we can communicate with the English police. It’s all quite illegal, of course! You have a car, I think, Mr. Greve! You will come with us, Dr. Collingwood? Good! Then let us start at once!” Robin intervened with a proposal that they should call _en route_ at his hotel to see if there were any telegrams for him. “Manderton knows I am in Rotterdam,” he explained, “and he promised to wire me the latest developments in the enquiry he is conducting.” “Miss Trevert should be fully recovered by this,” put in the doctor; “apart from a little sickness she is really none the worse for her disagreeable experience. If there was anything you wanted to ask her ...” “There is,” said Robin promptly. “Her reply to one question,” he explained, turning to Herr Schulz, “will give us the certainty that Parrish was murdered and did not commit suicide. It will not delay us more than five minutes to stop at her hotel in passing, We will then call in at my place. We should be at the Villa within half an hour from now ...” “Gentlemen,” said Herr Schulz as they prepared to go, “I know my Mr. Victor Marbran. You should all be armed.”