This is the continuation of the story Willis started in Blackout. It follows the same three characters, Polly, Eileen and Mike as they try to return to the future from London of 1940. It picks up right where the previous part ended. As with the first part, the characters occasionally act in ways that are unexpected for history grad students in that they seem to be much more clueless about World War II than one would expect. They also begin questioning the theories behind time travel as they fear that they may have changed the course of events - every time there appears to be even a slight discrepancy between what they think they know, and they think they see happen, they begin to freak out. Mike is especially bad about this as he constantly thinks that he has somehow altered events in a bad way and lost the war. One other character flaw that they have, especially Mike and Polly, is their desire to protect the rest of the group by withholding information to prevent them from worrying. Mike and Polly think that Eileen is too fragile and wouldn't be able to handle the truth, though I think Eileen ends up being the strongest of the characters.
Polly has an extra worry - part of time travel is that the traveler can't be in the same time twice - she has already been present in the later part of WWII so if she has not returned to the future by the date she comes back to the past, she will die. While Mike and Eileen would like to return home, Polly is actually racing against a ticking clock.
This novel also focuses some on a few other characters: Collin is teenage boy from the future that has had a crush on Polly for awhile and promised her he would always find a way to save her if she was ever in trouble. Polly spends much of the novel thinking about him, and hoping that he will keep his promise. The history department head had already noticed some issues with time travel, and goes on a rescue mission himself to find his students. Binnie and Alf, Eileen's charges, continue to play a role, and there are many moments of just missed chances that the historians experience during their search for a way home. Like in Blackout, while I like Eileen, Alf, Binnie and the vicar, the characters tend to be rather superficial. The setting and idea behind the novel were enough to make up for the weaker characters for me, and I think I'm getting soft in my old age, because I was definitely touched by Eileen's outcome in the novel.