Avsnitt 1

September 1940: Brian Ash, a direct entry officer of the Royal Engineers after ten weeks of basic training at the Hampshire Depot, joins 97 Tunnelling Company. Without benefit of training as a bomb disposal officer, he is immediately put in charge of a section whose previous officer was killed by a bomb . The unexploded bombs they deal with have been armed by electrical fuses that activate after being dropped, but sometimes fail to go off on impact. If they fail to explode on impact, they can detonate when vibrations caused by movement or contact close the circuit . Under the tutelage of Sergeant James, he defuses a relatively straightforward type 15 fused bomb, but is dismayed to learn that the Germans have deployed an even deadlier fuse, the type 17, that is rigged with a clockwork long-delay detonator activated by the bomb's impact.