While investigating a report of a submerged aircraft in the Scottish loch of Lochnaglash, Biggles discovered that the aircraft carried the registration GB-XKL, the aircraft registered to Murray. According to Biggles' recollection of the case, the disappearence took place about 8 years before the discovery of the submerged aircraft i.e. in the 1950s. There were signs that the murder was deliberately planned over a period of time. Murray had taken flying lessons to get his "A" licence. While training, he started withdrawing money from his bank, some four thousand pounds in all, a few hundred pounds at a time. He then shot his wife, took off in a club aircraft and disappeared. As the flight took place in June, Biggles surmised that he must have ditched the aircraft in the loch.
While searching the shore of the loch, Biggles met a Mr Macrae, an eagle watcher from the Scottish Bird Protection Society who told Biggles that he lived in an ex-stalker's house in a glen, the only habitation in the vicinity. Macrae looked the part. He was described as a powerfully built man, black-bearded, wearing a kilt of Lovat tweed, carrying a Highland cromach and wearing a Laggan bonnet. However he made some mistakes which led Biggles to suspect he was not what he seemed. For one thing, he carried a black hilted commando knife, stuck in his stocking as a skean-dhu. For another, he did not at first mention a nearby old lodge which had once been a commando training school. When Biggles asked about the lodge, he said it was used by some troops but he did not know what troops they were. As Biggles put it, every unit leaves its mark, and the lodge certainly had evidence that it had once been the No. 7 Commando Training School.
Later Biggles confronted Macrae near his house, asserting that he was actually Alva Murray, wanted for questioning in connection with the murder of his wife. However Murray resisted arrest and backed into his house where he held Biggles and co. off with a twelve bore shotgun. The local police was brought in to assist but Murray shot himself rather than submit to arrest.