Poison for the Toff — John Creasey

Richard Rollison, otherwise known as the Toff, has become lethargic. Even his passion for solving difficult criminal cases seems to have waned. Aunt Gloria arranges a birthday party so as to cheer him up, but it ends in disaster as one of his souvenirs - a tube of arsenic - disappears, with the contents later re-appearing in the ice-cream. The Toff is spurred into action and the master investigator has to solve one of his most difficult cases ever.