"Now they see that we are off they will know that their game is up," Chetwynd said.

"I am not so sure of that, Dick; there are craft going every day to Antwerp and Flushing, and for anything we know some of them may be on board a craft already dropping down like ourselves by this tide. But even if we had twelve hours' start, by landing, say at Flushing, they would have time to cross by land to Amsterdam and get there before us."

"Yes, I suppose they would; anyhow, it is pretty certain that we shall not be troubled on the voyage."

"Yes, I never thought there was much danger of that, because even if they were on board they would see that you and I, being always together, could not be got rid of without an alarm being given."

Not until they were passing Greenwich did either of the detectives come near Mark, then as he and Dick were standing by the bulwarks, looking at the hospital, Chester strolled across the deck and, pointing to the building as if asking him some question about it, said: