What is the foreshadowing in "The Masque of the Red Death"?

The long list of precautions taken by the prince and his thousand healthy and carefree friends, immediately following the description of how deadly and awful the Red Death is, seems to foreshadow the uselessness of such precautions.  The abbey to which they retire is geographically isolated, far away from where the disease rages; it is surrounded by a strong and tall wall; it has gates made of iron; Prince Prospero's guests plan to weld the bolts shut so that the gates cannot even be opened; the abbey has been stocked with anything and everything they could possibly want while there; and, most damning of all is their resolution "to leave means neither of ingress nor egress to the sudden impulses of despair or of frenzy from within."  They have determined to leave no way in and no way out of the castle.  On the one hand, this might seem positive since no one with the disease could push their way in; on the other hand, however, no one will be able to escape the castle should danger arise.

Furthermore, the dread that the courtiers seem to feel every time the ebony clock strikes, but especially when it chimes for midnight, foreshadows their ultimate demise.  When they hear those chimes, "for a moment, all is still, and all is silent save the voice of the clock.  The [masqueraders] are stiff-frozen as they stand.  But the echoes of the chime die away -- they have endured but an instant -- and a light, half-subdued laughter floats after them as they depart."  Clocks are often associated with mortality (as it keeps track of time), as is midnight (since it is the death of day) and the color black (often symbolic of mystery and/or death.  When this terrible black clock announces the death of day, it seems as though the courtiers cannot help but be reminded of their own mortality, foreshadowing their coming end.