“My dear Lakington, it’s quite unnecessary. You underrate that young man....”

He disappeared into the house, and the others followed slowly. For the time being Hugh was safe, and with a sigh of relief he stretched his cramped limbs and lay back against the sloping roof. If only he had dared to light a cigarette....

III

It was half an hour before Drummond decided that it was safe to start exploring. The moon still shone fitfully through the trees, but since the two car watchers were near the road on the other side of the house, there was but little danger to be apprehended from them. First he took off his shoes, and tying the laces together, he slung them round his neck. Then, as silently as he could, he commenced to scramble upwards.

It was not an easy operation; one slip and nothing could have stopped him slithering down and finally crashing into the garden below, with a broken leg, at the very least, for his pains. In addition, there was the risk of dislodging a slate, an unwise proceeding in a house where most of the occupants slept with one eye open. But at last he got his hands over the ridge of the roof, and in another moment he was sitting straddlewise across it.

The house, he discovered, was built on a peculiar design. The ridge on which he sat continued at the same height all round the top of the roof, and formed, roughly, the four sides of a square. In the middle the roof sloped down to a flat space from which stuck up a glass structure, the top of which was some five or six feet below his level. Around it was a space quite large enough to walk in comfort; in fact, on two sides there was plenty of room for a deck chair. The whole area was completely screened from view, except to anyone in an aeroplane. And what struck him still further was that there was no window that he could see anywhere on the inside of the roof. In fact, it was absolutely concealed and private. Incidentally, the house had originally been built by a gentleman of doubtful sanity, who spent his life observing the spots in Jupiter through a telescope, and having plunged himself and his family into complete penury, sold the house and observatory complete for what he could get. Lakington, struck with its possibilities for his own hobby, bought it on the spot; and from that time Jupiter spotted undisturbed.

With the utmost caution Hugh lowered himself to the full extent of his arms; then he let himself slip the last two or three feet on to the level space around the glass roof. He had no doubt in his mind that he was actually above the secret room, and, on tip-toe, he stole round looking for some spot from which he could get a glimpse below. At the first inspection he thought his time had been wasted; every pane of glass was frosted, and in addition there seemed to be a thick blind of some sort drawn across from underneath, of the same type as is used by photographers for altering the light.

A sudden rattle close to him made him start violently, only to curse himself for a nervous ass the next moment, and lean forward eagerly. One of the blinds had been released from inside the room, and a pale, diffused light came filtering out into the night from the side of the glass roof. He was still craning backwards and forwards to try and find some chink through which he could see, when, with a kind of uncanny deliberation, one of the panes of glass slowly opened. It was worked on a ratchet from inside, and Hugh bowed his thanks to the unseen operator below. Then he leant forward cautiously, and peered in....

The whole room was visible to him, and his jaw tightened as he took in the scene. In an armchair, smoking as unconcernedly as ever, sat Peterson. He was reading a letter, and occasionally underlining some point with a pencil. Beside him on a table was a big ledger, and every now and then he would turn over a few pages and make an entry. But it was not Peterson on whom the watcher above was concentrating his attention; it was Lakington—and the thing beside him on the sofa.

Lakington was bending over a long bath full of some light-brown liquid from which a faint vapour was rising. He was in his shirt sleeves, and on his hands he wore what looked like rubber gloves, stretching right up to his elbows. After a while he dipped a test-tube into the liquid, and going over to a shelf he selected a bottle and added a few drops to the contents of the tube. Apparently satisfied with the result, he returned to the bath and shook in some white powder. Immediately the liquid commenced to froth and bubble, and at the same moment Peterson stood up.