“Good gracious!” Tish cried.  “The girls have gone into the tent!  And somebody’s working at the stove.  The impertinence!”

Our situation was acutely painful.  We could do nothing but watch.  We called, but our voices failed to reach them.  And Aggie took a chill, partly cold and partly fury.  We sat there while they ate the entire supper!

They were having a very good time.  Now and then somebody would go into the tent and bring something out, and there would be shrieks of laughter.

[We learned afterward that part of the amusement was caused by Aggie’s false front, which one of the wretches put on as a beard.]

It was while thus distracted that Aggie suddenly screamed, and a moment later Mr. McDonald climbed over the side and into the boat, dripping.

“Don’t be alarmed!” he said.  “I’ll go back and be a prisoner again just as soon as I’ve fired the engine.  I couldn’t bear to think of the lady who fell in sitting here indefinitely and taking cold.”  He was examining the engine while he spoke.  “Have visitors, I see,” he observed, as calmly as though he were not dripping all over the place.

“Intruders, not visitors!” Tish said angrily.  “I never saw them before.”

“Rather pretty, the one with the pink cap.  May I examine the gasoline supply?” There was no gasoline.  He shrugged his shoulders.  “I’m afraid no amount of mechanical genius I intended to offer you will start her,” he said; “but the young lady—­Hutchins is her name, I believe?—­will see you here and come after you, of course.”

Well, there was no denying that, spy or no spy, his presence was a comfort.  He offered to swim back to the island and be a prisoner again, but Tish said magnanimously that there was no hurry.  On Aggie’s offering half of her tarpaulin against the wind, which had risen, he accepted.

“Your Miss Hutchins is reckless, isn’t she?” he said when he was comfortably settled.  “She’s a strong swimmer; but a canoe is uncertain at the best.”

“She’s in no danger,” said Tish.  “She has a devoted admirer watching out for her.”

“The deuce she has!” His voice was quite interested.  “Why, who on earth—­”

“Your detective,” said Aggie softly.  “He’s quite mad about her.  The way he follows her and the way he looks at her—­it’s thrilling!”

Mr. McDonald said nothing for quite a while.  The canoe party had evidently eaten everything they could find, and somebody had brought out a banjo and was playing.

Tish, unable to vent her anger, suddenly turned on Mr. McDonald.  “If you think,” she said, “that the grocery list fooled us, it didn’t!”

“Grocery list?”

“That’s what I said.”

“How did you get my grocery list?”

So she told him, and how she had deciphered it, and how the word “dynamite” had only confirmed her early suspicions.

His only comment was to say, “Good Heavens!” in a smothered voice.