“That’s right,” said Carter despondently.  “There’s nothing except the fact that Dean and the girl think they saw him in British uniform.  Why didn’t they follow and make sure?”

“They tried to,” said the chief, “but he gave them the slip.  I’m inclined to believe they were mistaken.  More than likely it was a chance resemblance.  Lots of Britishers of the Anglo-Saxon strain look much like Germans, and a uniform makes a big difference in a man’s appearance.  I’m afraid there’s nothing in that.”

“But both saw the man—­Dean and Miss Strong,” protested Carter.

“The trouble is,” observed Fleck, “that Dean is getting infatuated with the girl.  A young man in love is not a keen observer.  Anything she thinks she has seen he’ll be ready to swear to.  I hope the girl keeps her head.  Lovers don’t make good detectives.”

“I have watched them together,” said Carter.  “I’ll admit he’s struck on her, but I don’t think she cares a rap for him.  She’s too keenly interested in Frederic Hoff.”

“What do you mean by that?” asked the chief sharply.

“You can depend on her all right.  She’s patriotic through and through.  She’s the kind that would do her duty, no matter what it cost her.  All I meant is that Hoff’s the type that interests women.  He’s got a way about him.  The fact that he’s a spy, in peril most of the time, gives him a sort of halo.  I never knew a daring young criminal yet that didn’t have some woman, and often several of them, ready to go the limit for him.  All the same, I’m sure we can trust Miss Strong.”

“We’ve got to,” growled Fleck, “for the present at any rate.  Is everything fixed for the search this afternoon?  What have you done to get the superintendent out of the way?  He’s not to be trusted.  His name is Hauser.”

“I’ve got him fixed.  Jimmy Golden, my nephew, who has helped us in a couple of cases, is a lawyer.  He has telephoned to Hauser to come to his office this afternoon.”

“Suppose he doesn’t go?”

“He’ll go all right.  Jimmy ’phoned him that it was about a legacy.  That’s sure bait.  Jimmy will make Hauser wait an hour, then keep him talking half an hour longer.  That will give us plenty of time.”

“Then there’s the woman—­the servant, Lena Kraus.”

“She goes to the roof every Wednesday while the Hoffs are away to signal.  Other days they apparently do the signalling themselves in some way we haven’t caught on to yet.  She always goes up about three o’clock and—­”

“Suppose she comes down unexpectedly and catches you?  We can’t have that happen.  That would put them on their guard.”

“She won’t surprise us.  I’ve got a trick up my sleeve for preventing that.”

“Go to it, then,” said the chief, and Carter went on his way rejoicing.

Ever since he had been informed that the search of the Hoffs’ apartment was to be intrusted to him Carter had been in a state of exuberant delight.  He fairly revelled in jobs that required a disguise and he welcomed the opportunity it gave him and his assistants to don the uniform of employees of the electric light company.  He even made a point of arriving that afternoon at the apartment house in the company’s repair wagon, the vehicle having been procured through Fleck’s assistance.