The author of this one was clearly very impressed with having an incredibly tough granny, or maybe elderly aunt, as a small child, because the book is basically post-holocaust My Incredibly Tough Granny vs. Tamurlaine's Hordes.
The Incredibly Tough Granny, with the help of a friendly Native American shaman working Native American magic on the former site of a Superconducting SuperCollider, summons three heroes from the past to help her fight the hordes; Stonewall Jackson, George S. Patton, and Amelia Earhart. (Also a carnivorous
Triceratops egg which is hatched by her pet bald eagle.)
Two of these heroes are going to go back at the end of the book and one is going to stay in the future. Now, just how much tension do you think there is going to be in guessing which ?