[These notes were made in 1990:]. Though this looks like any other Allingham mystery, and features the self-effacing Campion, it is actually a venture into science fiction. The premise is that a small metallic device placed over the jugular assists people - especially children - to engage in telepathy. Allingham, having introduced this device (plot and metallic), makes no effort to debunk it or show it to be fraudulent in the end. Instead, she involves Campion (one of whose young relatives-by-marriage discovers the device) in a web of spies, counter-spies, secret experimental laboratories and criminals of all descriptions. The children are put in jeopardy, then satisfactorily recovered, and in the process we learn a little more about domesticity, Campion-style.
