The Exaltationist Saga IV

Poul Anderson, Time Patrol (New York, 2006).

Manson Everard of the Time Patrol learns about Wanda Tamberly by interviewing Helen Tamberly in 1885. Castelar of the Conquistadors learns about Wanda by interrogating Stephen Tamberly in 2937 BC.

Everard interviews Wanda in 1986, seeking clues about her Uncle Stephen's disappearance. Castelar kidnaps Wanda in 1987 so that she can guide him to a twentieth century armory.

The Tamberlys have two problems:

Stephen is stranded in 2937 BC;
Wanda is Castelar's prisoner, first in 1435, then in 1987.

In some time travel stories, like "Ivory, and Apes, and Peacocks," time travelers who have visited another period remain in that period for the duration of the narrative whereas, in a story like "The Year Of The Ransom," they move around a lot. Poul Anderson, beginning with more straightforward short stories in the 1950's, wrote longer and more complicated time travel plots in the '80's and '90's.