âAre you sure, Miss Tice, there was nothing else stolen from this room? Like hypodermic syringes or sedatives?â
âPositive,â the nurse assured him.
Frank spoke up. âJoe and I hope to solve this mystery on our own, Chief, but weâd like to brief you on it.â
The boys gave the officer a concise account, ending with their plan for possibly picking up a clue on tape.
âGood idea,â the chief said. âIâll do my best to help you. At least we can have an alert sent out for anyone resembling the intruder. Iâm posting a guard on this floor, and also will have this jacket analyzed in our lab.â
âThanks, Chief. Thatâs swell,â said Frank.
When the police had gone, Frank asked the nurse, âDid you have much of a tussle with the thief?â
âNo. When I grabbed his mask, he pushed me aside and ran.â
âWould you mind showing me your fingernails?â Frank requested.
The woman held out her hands. Using a pocket flashlight, Frank carefully scrutinized both hands. Suddenly he said, âHereâs somethingâa wisp of black hair!â He pointed to the nurseâs right forefinger.
âWhy, I never noticed it!â she exclaimed.
Miss Tice removed the tiny hair, which Frank folded in a sheet of white paper and put in his slacks pocket.
The young sleuths took the recorder, thanked the nurse for her cooperation, and left the room. Outside Mr. Hardyâs door was a patrolman whom the boys knew. He assured them, âNo sneak thief will get by Tim Callahan.â
The Hardys grinned. âI believe it, Mike,â said Joe.
As soon as they arrived home, Frank and Joe went directly to their lab. Frank was first to study the strand of hair under a powerful microscope. âJoe! Take a look!â
His brother did so. âSay! That hairâs gray near the roots. Itâs dyed black!â Joe was exuberant. âMatlackâs for sure. I bet the mustache is phony too.â
Both boys were exhilarated by the thrill of their discovery. Now for the tape. Did it, too, hold a valuable clue?
Soon the tape was revolving on the machine, and although Frank had turned the volume up full, there were great stretches of silence. These were interspersed by Mr. Hardyâs mumbling, which was indecipherableâexcept one word that came through with relative clarity.
âWhatâs that, Joe? Something like âlicksâ? Iâll play it back.â The strange word, or part of a word, came over three times.
Joe listened intently. âSounds to me like Felix,â he said.
âCould be. Perhaps Felix is a henchman of Matlackâs.â Frank shut off the machine and Joe telephoned police headquarters. Chief Collig was still there.
âChief,â said Joe, âdo you know of any underworld character named Felix? We think thatâs a word which came over on the tape.â
Collig said this did not ring a bell, but he would check his files thoroughly. âIâll let you know.â
When Frank and Joe returned to the house, they quietly went into the kitchen and made cocoa. As they drank, the brothers discussed the nightâs events. Suddenly Joe put down his cup. âFrank! In all the excitement we forgot to check the airport for the plane that tailed Jack!â
Frank immediately telephoned Bayport Airport, and learned that one other plane from Kentucky, an air taxi out of Louisville, had asked for landing permission the previous afternoon. It had taken off a short while ago.
âJoe, that Kentucky pilot must have been the one who tailed Dadâs plane!â Frank exclaimed. âWish we couldâve nabbed him.â
âWhere is he headed?â Joe asked.
âLa Guardia Airport in New York.â Because it was too late for the Hardy boys to do anything further, they tumbled into bed. Early the next morning Aunt Gertrude summoned them to breakfast. Although the bacon and scrambled