It was a small matter; but it magnified itself as he dwelt upon it.

He suspected that Alice had deceived him.

He sharply questioned Father Beret, only to be half convinced that the good priest told the truth when he said that he knew nothing whatever on the subject beyond the fact that the banner had mysteriously disappeared from under his floor.
Captain Farnsworth scarcely sympathized with his chief about the flag, but he was nothing if not anxious to gain Hamilton's highest confidence.

His military zeal knew no bounds, and he never let pass even the slightest opportunity to show it.

Hence his persistent search for a clue to the missing banner.