Malcolm Quarrie was one of the men who both Delia Morrison and Vincent Tuck referred to as spending a great deal of time with Alexander Roby in 1925. His other associates being Lawrence Bacon, Montague Edwards and Michael Coombes.

Referred to by Alexander Roby during his monologue to Dr Bartlett, the following is stated:

• Roby does not know where Quarrie is.
• He may be attempting to 'bring' The King in Yellow.
• It appears Quarrie disagreed with Roby and Edwards on one or more issues.
• Quarrie believes that the King in Yellow has called himself The White Acolyte.

Roby also asks Bartlett to pass on a stanza of poetry to Quarrie as a warning or piece of advice:

The stars that burn their charcoal death,
Shrink back, they feel the hoary breath,
Of he who ransoms great Carcosa.
He flees where queen and prophet met,
Where twin suns fall but never set,
Escapes the tomb of lost Carcosa.

Throughout the adventure, numerous individuals mentioned Quarrie:

• According to Vincent Tuck who saw him in 1925, Quarrie was about 35, upper middle class with black hair and a slim build. A scientist, he worked at the Royal Society in Piccadilly and lived alone at 12 Moreton Street in Westminster.
• Malcolm's wife, Hillary Quarrie, apparently lives at Nug's Farm in the West Country. According to the letters found at Quarrie's former address he was estranged from Hillary.
• Wilfred Gresty's letters connected Hillary to a man called Atkinson, and Gresty's ambitions. The full story of The Quarrie family's involvement with the Goatswood cult can be found on here.
• Aleister Crowley believed that Quarrie had gone to Italy in search of The Brothers of the Yellow Sign.

The first letter gave his reasons for breaking with Bacon and his circle and told of his planned 'Pilgrimage of Grace' to bring Hastur to Earth. It gives his location as Milan and says he can be reached by letter through the Thomas Cook offices in that city.

The second letter, far more recent, explains that Malcolm is about to set out on his 'Pilgrimage' and gives specific contact details through Thomas Villiers at the shipping office of Giuseppe Colombo in Milan.

In Milan, Thomas Villiers revealed that he and Quarrie had travelled to Italy together, having broken with the Bacon group after Springer Mound and met the Brothers of the Yellow Sign in Rome, prior to joining a splinter group of the Brotherhood in Milan, with Colombo and professor Roberto Anzalone.

Quarrie and Anzalone formed an expedition, ostensibly to Tibet, but whose true destination appears to be in the Nepalese kingdom of Mustang. Quarrie left for the Himalaya some weeks ago and according to his letter to his wife expected to encounter The King in Yellow at some time after December.

Quarrie was finally encountered on the other side of the gate from Drakmar to Leng. There is was that surrounded by their Tcho-Tcho captors the investigators finally caught up with their ‘quarry’.

Astonished to see Westerners, Quarrie at first assumed they were fellow Pilgrims, but it soon became obvious that these men had come all this way to stop him, not aid him.

They told Quarrie of their dealings with Roby, Bacon and Edwards and of course of their meeting with Hillary Quarrie, and her message to her husband. They also gave Quarrie the warning that Roby told them to give him. He gave a wry smile and said this was all ‘a test of faith’.

Quarrie trekked across Leng with the investigators and their Tcho-Tcho escorts, and from there spent 2 days wandering the dark halls of the Upper House with them – all this time they tried to persuade him that what he wished to do was dangerous, but his religious fervour was impenetrable.

Eventually, while Quarrie sat explaining his credo to Nathaniel Browne, who was finding it more convincing with every passing minute, Umberto walked up to Quarrie and, without warning, put a bullet through his head.

Almost as soon as Quarrie was dead, Browne realised that Malcolm had been attempting to sway him by the same sorcerous means used on Major Delnegro. With Quarrie gone, the power of his arguments quickly faded.