In the classic British film The Third Man, the central mystery concerns whether the elusive title character, played by Orson Welles, is alive or dead. Journalist John Geiger makes no mention of that movie in his book, but the Third Man he writes about is also something of a ghost.

Drawing on diary entries, first-person interviews, and a patchy body of scientific literature, The Third Man Factor is an exhaustive account of the so-called Third Man phenomenon, in which people report sensing a ghostly presence during extreme physical and mental duress. Examples include a botched Everest summit and a Second World War shipwreck. (Why the Third Man and not the Second Man? The explanation is too convoluted to recap here.)

The stories’ protagonists have one thing in common: they all faced seemingly insurmountable odds, and they all somehow miraculously survived after encountering “sensed presences” that offered not only “companionship, but also useful information or advice, and at other times seem[ed] to take a direct hand in improving the chances of survival.” Such encounters are so common, in fact, that they have become lore for modern-day adventurers: “the Third Man is nearly as much a part of high altitude climbing as supplementary oxygen,” one mountaineer claims.

For the armchair explorer, however, the wealth of anecdotal evidence is a bit overwhelming, as even the most expansive narratives, such as Sir Ernest Shackleton’s harrowing crossing of the South Georgia Islands, are given a scant few pages to develop. Even more puzzling are Geiger’s tepid speculations about the Third Man’s otherworldly origins, tossed in from time to time as unexamined asides. (“These occurrences suggest a radical idea – that we are never, really, truly alone, that we can summon someone – some other – in certain situations.”)

The Third Man Factor is a unique mix of adventure and the transcendental, but the catalogue of uncanny experiences never really hooks the reader. After all, the most memorable ghost stories aren’t always the most plausible or best researched ones. It’s the telling, not the tale, that stays with you.