Michael Gilbert 
Mr Calder And Mr Behrens [PDF ebook] 

More short stories about the deceptively harmless but sometimes lethal pair of agents, Calder and Behrens, who are also met in ‘Game Without Rules’. Calder lives in Kent with a golden deerhound named Rasselas, whilst Behrens lives with his aunt and keeps bees. No one suspects they are in fact agents for the British security services and that, if necessary, they are prepared to kill. The first story deals with Behrens pre-Calder days inside wartime Germany, and the adventures progress through time to the late twentieth century. Ruthless in defence of the Crown, friends and those deemed innocent, but equally ruthless in disposing of wrongdoers and enemies of the state, the conclusive nature of which is arrived at through logic and reasoning. A lovable lethal pair!