From the author of Blackout comes the final thrilling instalment of the enormously entertaining story of time travel, war and the deeds of ordinary people who shape history.

In Blackout, award-winning author Connie Willis returned to the time-travelling future of 2060 and sent three Oxford historians to World War II England: Michael Davies, intent on observing heroism during Dunkirk; Merope Ward, studying children evacuated from London; and Polly Churchill, posing as a shop girl in the middle of the Blitz. But the three become unexpectedly trapped in 1940, struggling to go home they also have to survive, as Hitler's bombers attempt to pummel London into submission.

Now the situation has grown even more dire. Small discrepancies in the historical record seem to indicate that one or all of them have somehow affected the past, changing the outcome of the war. The belief that the past can be observed but never altered has always been at the core of time-travel theory - but suddenly it seems that the theory is horribly, tragically wrong.

Meanwhile, in 2060 Oxford, the historians' supervisor, Mr Dunworthy, and seventeen-year-old Colin Templer, who nurses a powerful crush on Polly, are attempting the seemingly impossible feat of trying to find three missing needles in the haystack of history.

All Clear is more than just the triumphant culmination of the adventure that began with Blackout. It's Connie Willis's most humane, heartfelt novel yet - a clear-eyed celebration of faith, love, and the quiet, ordinary acts of heroism and sacrifice too often overlooked by history.