18,244 BC II

During the first part of that short period in 18,244 BC, the secret Time Patrol group is trying to prevent timeline alpha, whereas during the concluding part of that same period, they are trying to prevent timeline beta, which replaces alpha. If, when the second task has been completed, Everard returns to that short period and then travels futureward, will he remain in the Time Patrol timeline or instead return to one of the two divergent timelines?

I think that the answer is that an Everard who knows of a divergent timeline but has not yet prevented it will enter the divergent timeline whereas an Everard who has prevented it will not enter it even if he travels futerward from the exact same moment as his younger self who did enter the divergent timeline.

Suppose that one of the time machines that had entered timeline alpha was not a timecycle but a large, enclosed "time-liner" carrying a crew of several hundred. Suppose further that Everard, having prevented timeline alpha, travels back and enters the time-liner before its departure. Will he then enter the divergent timeline that he has prevented? (Anyone wanting to escape from the Time Patrol could enter such a timeline and live the rest of his life within it.)

In an earlier divergent timeline, Everard had said:

"'...the Patrol and the Danellians are wiped out. (Don't ask me why they weren't "always" wiped out; why this is the first time we came back from the far past to find a changed future. I don't understand the mutable-time paradoxes. We just did, that's all.')"
-Poul Anderson, Time Patrol (New York, 2006), p. 187.

The real reason is, of course, that the author has decided to write a Time Patrol story in which the past is changed but Everard cannot say that - although he comes so close to saying it that this passage might count as "metafiction," i.e., as a work of fiction that somehow acknowledges its own fictional status.

Guardians Of Time is comparable to, although much better than, Isaac Asimov's Foundation Trilogy in which history also diverges from its preferred course when one of Hari Seldon's psychohistorical predictions goes wrong.