Probably the most highly regarded episode of Quiet, Please is "The Thing on the Fourble Board" (August 9, 1948), about an oil-field worker who encounters a mysterious subterranean being hiding on the derrick's catwalk. The unusual title is a bit of oil worker argot: the "fourble board" of an oil derrick is a narrow catwalk that is as high up as four lengths of drilling pipe placed vertically (two lengths of pipe are a "double", three are a "thribble" and four are a "fourble.")
The story's effectiveness has led some fans to label the episode one of the best radio horror programs ever broadcast. Richard J. Hand of the University of Glamorgan notes that "The Thing on the Fourble Board" is not only cited as the finest example of radio horror, but occasionally cited as one of the best examples of radio drama as a whole. Especially effective was Cecil Roy's vocal performance as the creature. Though she performs only very briefly, Roy's vocal (barely recognizable as human) was cited by Dunning as still startling and chill-inducing even after decades.
According to Hand, Cooper's script for the episode was dizzyingly multilayered, blending authentic details of oil rig workers' daily activities, with elements of what might be termed "subterranea" or Hollow Earth lore, yet managing to faintly invoke nautical stories like the kraken.