Faculty Lodge

We learn a lot more about the Time Patrol Academy in The Shield Of Time. At night, luminous paths across campus lead Wanda to Faculty Lodge, where she finds:

a gravity shaft;
a soft, warm, flesh-like floor;
light from every direction;
a disappearing, reappearing door;
sky-revealing, stars-enhancing ceilings;
framed moving three-dimensional scenes;
music, maybe Japanese.

(Gravity shafts replace lifts/elevators in other futuristic fictions by Poul Anderson. The scenes, whether recorded or live, are of cliffs above sea and a mountain at dawn.)

Wanda's host, Guion, says:

"'There are occasions when we know only that the web [of world lines] is troubled, not where or when the source of the disturbance lies; for that source perhaps does not exist in our yet, our reality. We can only try to trace it back up the threads -'" (p. 135).

If Patrol agents do trace a disturbance as far as they can, then there are two things that they might find:

(i) a time traveler who arrives in a time shuttle or on a timecycle without having departed from any earlier or later time in this timeline and who bears memories of another timeline even though the latter is regarded as nonexistent;

(ii) an event that contradicts the memories of time travelers from its future.

(ii) is the random factor. Thus, a Time Patrolman based in 1137 knows that King Roger of Sicily should not die in this year but is then told that Roger has died in battle. An event has changed without any intervention by a time traveler: impossible to predict or prepare for but nevertheless possible and noticed only by some time travelers. Scary stuff.