Hangman's Curfew

A friend staying with distinguished psychoanalyst and sometime detective Mrs Bradley is alarmed by a chance meeting with a pale young man who claims his uncle is being poisoned - is there a detective who could help discover the culprit? Mrs Bradley is soon on the case, but upon investigation it seems the uncle is in the best of health. But then the old man does indeed die suddenly, followed by his nephew, and Mrs Bradley finds herself in the murderer's firing line.