A guilty secret. A gruesome murder. A DEADLY MOTIVE. Deadly Motive is the second book in the DS Jack Mackinnon crime series. A man is found poisoned by the deadly toxin aconite. A note found at the scene leads Detective Sergeant Jack Mackinnon to a University of Oxford laboratory, where staff and students are desperate to hide their association with the victim. After an arrest is made, his colleagues believe the case is all but closed ... but Mackinnon's nightmare is only just beginning.