1.[The Man of Mystery]
2.[A Secret Service Case]
3.[The High Flyers]
4.[The Mad Pursuit]
5.[Death Rides the Air]
6.[Another Visitor]
7.[On the Trail of “Mr. Seven”]
8.[A Sudden Attack]
9.[In the Valley]
10.[“Mr. Seven’s” Secret]
11.[Rescue from the Air]
12.[Against Time]
13.[Eastward Bound]
14.[The S-18]
15.[An Unknown Intruder]
16.[The First Test]
17.[On the Bottom]
18.[The Missing Cook]
19.[The Warning Note]
20.[Isle of the Singing Trees]
21.[The Battle with the Iron Mate]
22.[Trapped]
23.[Desperate Hours]

The Treasure Hunt of the S-18

CHAPTER ONE
The Man of Mystery

The high pitched drone of a wasp engine sounded over the municipal field at Atkinson and Tim Murphy, famous flying reporter of the Atkinson News, poked a grease-smudged face out from behind the cowling of a trim biplane and squinted skyward. Against the brilliant sky of the late summer afternoon was the outline of one of the new high speed transports of the Red Arrow Transcontinental Air Express Company.

The Day Express, Chicago to the west coast, was swinging around, preparatory to landing on the smooth, crushed-rock runway. Tim watched with appreciative eyes. The new transports, capable of winging their way from coast to coast at better than three miles a minute, always fascinated him. He envied the trim, clear-eyed young chaps who sat at the controls while they in turn would have been willing to exchange their daily routine for the adventurous news assignments which often came Tim’s way.

The twin motors, mounted in nacelles projecting from the sturdy wing, idled as the ship drifted downward to touch lightly on the runway and roll smoothly toward the main hangar.

“Star gazing again?” asked a quiet voice at Tim’s elbow.

The flying reporter turned quickly. Carl Hunter, manager of the airport, was beside him.

“I always get a thrill watching those high speeds come in. There’s something in it that gets into my blood and makes it tingle.”