Ordinal Unknown

Two groups of time travelers return from missions to change the past, arriving at almost exactly the same time, and each returning from a world where what the other eliminated was present. How could this be? Surely one group or the other must have gone (if you'll forgive the expression under the circumstances) first? The groups sit down to unwind this riddle—and end up posing several more in the process—and to describe the strange time and times they are respectively from. Come listen! Coffee, tea and muffins will be served.

"Ordinal Unknown" is the third story in the second movement of the Retcon series (the twelfth overall). It builds upon the earlier stories, but is also an independent novella that can be read and enjoyed on its own.