"Even this donkey might be pressed into service," continued the flight-sub, indicating Butterfly, who, having been placed "under arrest," was browsing on the green surrounding the flagstaff. "Although I've had enough of donkeys to last me for some considerable time."
Little knowing that the animal under discussion was the self-same one that had given him the slip at Barborough, Billy, accompanied by his two comrades, entered the detached building known as the look-out house. The ground floor was utilised as a kind of store, where arms and nautical gear were kept. Above was a large room furnished like an office, in which was a telephone as well as a large telescope mounted on a tripod so as to command a clear view of the sea. Being night the windows were closely shuttered, while double doors prevented any stray beams from escaping into the night.
"Up aloft, sir," said the scout. "I'll telephone through and see if a trap or a car can be sent from Tongby. This is our mess room," he explained. "There's a good fire going. Hullo! There's some one here already. I think it's the gentleman who told us about the spy."
Seated on either side of the roaring fire were Peter Barcroft and Philip Entwistle. The former's face was turned away from the door, and at first Billy failed to recognise his parent. Nor did he the vet., for Entwistle's face was elaborately and liberally embellished with sticking-plaster, as the result of First Aid on the part of the Scouts following their determined onslaught on the brink of the cliff.
Entwistle had taken his gruelling in rightdown good part. He was still under nominal arrest, for having been made a prisoner he could only be released at the order of a superior officer. Already a report had been telephoned through and a reply was momentarily expected.
"I am not going to explain the whole business to you, Barcroft," said the vet, when Peter expressed his regret at the attack upon his neighbour, and still more so his astonishment at finding him under most peculiar circumstances on the cliff at Scarby. "Some day, perhaps. I had information—no matter how—that some one was in traitorous communication with enemy submarines. To bring home proofs of the principal's guilt it was necessary to tackle his subordinate. Unfortunately my plans were upset by the somewhat injudicious intervention of these youngsters—commendable as regards pluck and all that, but nevertheless it spoilt my investigations."
"I didn't know that you were in the detective line," remarked Peter.
Entwistle shrugged his shoulders.
"Perhaps I had better not commit myself by answering your question," he replied with a laugh that ended in a wince. It was no easy matter to smile with one's face smothered with sticking-plaster. "I hope you understand my reluctance to say anything more on the matter."
Peter nodded.