Three bland archaeology graduate students, one of whom envisions himself as a knight, are
sent back to 14th-century France to rescue their professor. The novel mentions a multiverse
model of time-travel, but gives no explication (nor does it enter the plotline); the most
interesting characters and developments appear for a few pages and are never again heard of
(at least not in this universe).
I don’t mean time travel at all. Time travel is impossible. Everyone knows that.