C.B. knocked his pipe out, and went on. 'Apparently Lothar came through on their psychic wave about four o'clock this morning. He was doing a check up to make sure that Otto did not mean to let him down and, when he found that Otto was still there in Wales, he threatened to put a curse on him that would kill him. Otto protested that he had meant to come but had been prevented at the last moment. When he had gone to the top boy at the Station, Sir Charles Remmington-Rudd, to tell him that he meant to go to London for the week-end, Sir Charles had said he could not let him. A signal had just come in to notify them that an American egg-head was flying down that afternoon to spend a couple of nights at the Station. The Yank is a fuel expert and, as Otto is our star fuel boffin, he had to be there to do the honours.'

'I get it,' Barney put in. 'Otto realized that he dared not ignore his boss's order to stay put, as if he had they would have tumbled to it that there was something fishy about his trip to London. There would have been a hue and cry after him. We should have been alerted to pick him up this end and have him tailed. He saw himself being pinched when he kept his appointment with Lothar and, as he would have had the fuel formula on him, both of them would have been for the high jump.'

'Precisely. That's what he told Lothar. Whether Lothar thought he was lying or not we don't know. Anyway, he made it plain that he was not prepared to wait much longer. He indicated that, since the mountain would not come to him, he meant to go to the mountain. He demanded that Otto should select some lonely spot a few miles outside the Station, which it would be easy for him to find, and that he should meet him there with the formula on Sunday afternoon. Otto gave him as a rendezvous a place called Lone Tree Hill, and described its situation. Lothar said that he would be there sometime between two o'clock and four, and that Otto was to go there dressed in an old raincoat and beret, so that he would be easily recognizable from a distance. He added that, if Otto failed to turn up, or betrayed him afterwards, he would be dead in nine days. And that is that.'

Barney nodded. 'I don't wonder you are worried, Sir. It's going to be a tricky business to draw a cordon round an exposed hill-top without Lothar spotting what you are up to.'

'I know; but I may decide to intervene before they meet. Anyway, it's no good trying to settle on a plan before we've talked the whole thing over with Forsby.'

'We!' Barney echoed.