“I think the best thing I can do,” said Gentleman Jack smoothly, “is to go and telephone for the police.”

“You think of everything, Lord Wisbeach,” said Mrs. Pett.

“Not at all,” said his lordship.

Jimmy watched him moving to the door.  At the back of his mind there was a dull feeling that he could solve the whole trouble if only he could remember one fact which had escaped him.  The effects of the blow he had received still handicapped him.  He struggled to remember, but without result.  Gentleman Jack reached the door and opened it:  and as he did so a shrill yapping, hitherto inaudible because of the intervening oak and the raised voices within, made itself heard from the passage outside.  Gentleman Jack closed the door with a hasty bang.

“I say that dog’s out there!” he said plaintively.

The scratching of Aida’s busy feet on the wood bore out his words.  He looked about him, baffled.

“That dog’s out there!” he repeated gloomily.

Something seemed to give way in Jimmy’s brain.  The simple fact which had eluded him till now sprang into his mind.

“Don’t let that man get out!” he cried.  “Good Lord!  I’ve only just remembered.  You say you found me breaking into the safe!  You say you heard a noise and came down to investigate!  Well, then, what’s that test-tube of the explosive doing in your breast-pocket?” He swung round to Miss Trimble.  “You needn’t take my word or his word.  There’s a much simpler way of finding out who’s the real crook.  Search us both.”  He began to turn out his pockets rapidly.  “Look here—­and here—­and here!  Now ask him to do the same!”

He was pleased to observe a spasm pass across Gentleman Jack’s hitherto composed countenance.  Miss Trimble was eyeing the latter with sudden suspicion.

“Thasso!” she said.  “Say, Bill, I’ve f’gott’n y’r name—­’sup to you to show us!  Less’ve a look ‘t what y’ got inside there.”

Gentleman Jack drew himself up haughtily.

“I really could not agree to—­”

Mrs. Pett interrupted indignantly.

“I never heard of such a thing!  Lord Wisbeach is an old friend—­”

“Less’f it!” ordered Miss Trimble, whose left eye was now like the left eye of a basilisk.  “Y’ gotta show us, Bill, so b’ quick ’bout ’t!”

A tired smile played over Gentleman Jack’s face.  He was the bored aristocrat, mutely protesting against something that “wasn’t done.”  He dipped his slender fingers into his pocket.  Then, drawing out the test-tube, and holding it up, he spoke with a drawling calm for which even Jimmy could not help admiring him.

“All right!  If I’m done, I’m done!”

The sensation caused by his action and his words was of the kind usually described as profound.  Mrs. Pett uttered a strangled shriek.  Willie Partridge yelped like a dog.  Sharp exclamations came simultaneously from each of the geniuses.