From the Depths of Time, Part Two

The members of Valentinian's crew have been divided into groups at different points in history, from the French Revolution to the sinking of the Titanic, and in each time zone a Centaur invasion is imminent. But even with the help of unexpected allies, any attempt to defeat the Centaurs and their human-like androids is futile, and it seems there's nowhere in the whole galaxy to run where they won't be found, in any era.