It's little-known that there were THREE novels published from this TV series. The publisher really confused matters by, not only not mentioning that this is the novelization, but using the same cover picture as on the first original novel which inspired the TV series!

TIME BOMB The experimental nuclear missile was sent through the Time Tunnel—but something went wrong, and it wound up buried in the capital of a great nation, over a century ago! Now, excavation equipment was moving toward the site—any day a bulldozer blade might set it off, destroying a mighty city and plunging the world into war! Time travelers Tony Newman and Doug Phillips had only one chance to head off disaster—to go through the Time Tunnel and make the accident "unhappen." The trouble was, there was a war on in the past—and the bomb was in enemy territory....