The Sergeant reached this conclusion quickly, and, satisfied that any further investigation along this line would be worthless, reverted to his earlier quest—­the safety of Miss McDonald.  Merely to satisfy himself of her presence, he crossed the street and glanced in at the whirling dancers.  There were few loiterers at the doorway and he stood for a moment beside the guard, where he was able to survey the entire room.  Mrs. Dupont was upon the floor, and swept past twice, without lifting her eyes in recognition, but neither among the dancers, nor seated, could he discover Miss Molly.

Startled at not finding her present, Hamlin searched anxiously for the Major, only to assure himself of his absence also.  Could they have returned to the fort as early as this?  If so, how did it happen their guest was still present, happily enjoying herself?  Of course she might be there under escort of some one else—­Captain Barrett, possibly.  He would ask the infantryman.

“Have you seen Miss McDonald since supper?”

The soldier hesitated an instant, as though endeavoring to remember.

“No, I ain’t, now you speak of it.  She went out with that kid over there, and he came back alone.  Don’t believe he ’s danced any since.  The Major was here, though; Connors brought him a note a few minutes ago, and he got his hat and went out.”

Hamlin drew a breath of relief.  “Girl must have sent for him to take her home,” he said.  “Well, it ’s time for me to turn in—­good-night, old man.”

He tramped along the brightly illumined street, and out upon the dark road leading up the bluff to the fort, his mind occupied with the events of the evening, and those other incidents leading up to them.  There was no doubt that Miss McDonald and her father had returned to their home.  But what could he do to assist her?  The very knowledge that she had voluntarily appealed to him, that she had come to him secretly with her trouble, brought strange happiness.  Moreover his former acquaintance with Mrs. Dupont gave him a clue to the mystery.  Yet how was he going to unravel the threads, discover the motive, find out the various conspirators?  What were they really after?  Money probably, but possibly revenge.  What did the woman know which enabled her to wield such influence over McDonald?  What was the trap they proposed springing?  The Sergeant felt that he could solve these problems if given an opportunity, but he was handicapped by his position; he could not leave his troop, could not meet or mingle with the suspected parties; was tied, hand and foot, by army discipline.  He could not even absent himself from the post without gaining special permission.  He swore to himself over the hopelessness of the situation, as he tramped through the blackness toward the guard-house.  The sentinel glanced at his pass, scrutinizing it by the light of a fire, and thrust the paper into his pocket.  Hamlin advanced, and at the corner saluted the officer of the day, who had just stepped out of the guard-house door.