'To develop and manufacture a devastating and demoralising weapon, deliverable by air, hitherto unknown by mankind.' In 1933 when Nazi Germany was on the rise, this was the brief issued to the secret K1 research facility, to manufacture a weapon so terrifying to foreign nations that it would deter the use of any specialist weapons against the UK. But what if that weapon was too terrifying? What if the exercises, planned for use on animals, were so horrific that some of the researchers balked at the idea and began to rebel? This is the situation in Stephen F. Clegg's The Hallenbeck Echo where the impact of K1's appalling development continues up until 2007 and brings the police into direct conflict with MI5 as they try to uncover a horrific past which is governed by the Official Secrets Act until 2087. In Walmsfield, Lancashire, historic researcher Naomi Wilkes is asked to investigate the disappearance of a young woman. In London a strange bleeping is heard coming from behind the wall of a house that is being renovated.