One of the men was Jacob, but all three were busily engaged. Unfortunately it was not possible to hear what they were saying and what they were actually doing was puzzling enough. Each man had before him a large rucksack, which he was filling with square packages piled in the centre of the table. There were also some coils of wire and a number of unusual looking boxes and cylinders. One of the strangers was consulting a list and another something which David guessed to be an engineer's blue print. There was no sign of Mrs. Thurston or the twins, and David was wondering whether to go back and call Mr. Ingles when Tom's foot slipped and he lost his balance. Luckily David caught him as he fell forward and prevented his head from banging against the window. They were so alarmed by this narrow escape that they scuttled away from the window on to the grass under the trees.

"You silly ass," David muttered. "Why did you do that?"

"I couldn't help it. My foot had gone to sleep... I say, David, what are they doing? And who are those chaps?"

Before David could answer, Mr. Ingles loomed up out of the dark, and, taking them each by an arm, led them over towards the gate.

"Just a minute," he whispered. "Wait till we're out of earshot... Now then. I can see you've found something. Are those kids there? I couldn't discover anything at the back except that all the rooms, including what must be the kitchen, are dark."

David told him quickly what they had seen, and he said: "Stay here, Tom. Come over and show me the window, David. I want to see this for myself."

Left alone again, poor disgruntled Tom jabbed his hands in his pockets and did what he usually did when he was on his own - he did it without thinking - he whistled. Fortunately he whistled what had been in his mind a few minutes earlier - the peewit's lonely little call. Twice he sent out the Lone-Piner's call for help and the answer came unexpectedly. From somewhere near, but very muffled, came the short, warning bark of a dog. Tom, suddenly realizing what he had done, stiffened in anticipation. Would the others hear? And would someone in the house be warned? And was the dog Macbeth? It might not be!

Then David was at his side.

"Tom! That was Mackie. I know it was. They're somewhere in the house. I'm sure of it. Let's tell your uncle to go and bang on the door, and we'll jolly well go and get them out."

"Where is Uncle?"

"I left him looking through the crack. He'll be back in a sec. Here he is... "and he started to pour out an excited story till Mr. Ingles stopped him.