Mr. Calder and Mr. Behrens

Mr. Calder and Mr. Behrens are fictional counter-intelligence agents created by the British mystery and thriller writer Michael Gilbert. The characters appear in 24 short stories, most of which first appeared in either the British magazine "Argosy" or the American "Ellery Queen's Mystery Magazine". The stories were collected in two anthologies, "Game without Rules" (1967) and "Mr. Calder & Mr. Behrens" (1982). One story, "Double, Double", was later republished in an Ellery Queen paperback. Many involve finding and dealing with British traitors or deeply embedded foreign agents; a few take place in Europe; one particularly grim one is set in World War II, during which Mr. Behrens is the bomb-maker in a failed attempt to assassinate Adolf Hitler. The characters also appeared in 16 BBC radio plays, largely based on the short stories.
Gilbert, who was appointed CBE in 1980, was a founder-member of the British Crime Writers' Association. The Mystery Writers of America named him a Grand Master in 1988 and in 1990 he was presented Bouchercon's Lifetime Achievement Award. 
Biographical Information.
Gilbert's two agents are outwardly gentlemanly and urbane. Beneath their innocuous appearance, however, they are ruthless and exceedingly hard-boiled killers. They are long-time close friends who are unmarried and who live near each other in the vicinity of Lamperdown, Kent. Mr. Behrens lives at The Old Rectory, while Mr. Calder is at The Cottage, Hyde Hill. (Gilbert's own address, at which he lived for many years, and where he died at age 93, was Luddesdown Old Rectory, Cobham, Gravesend, Kent.)
Both Calder and Behrens were educated in various parts of Europe before World War II and speak a number of languages: Mr. Behrens is rated A+ for Standard-German and A for Standard-French, Standard Greek, Italian, and Russian. Mr. Calder is rated A for Standard Albanian and Hungarian and B for Standard-Greek, Italian, Arabic, and Russian.
Mr. Calder lives with Rasselas, his 128-pound Persian deerhound whom he has adopted from a dead adversary. Like his master, Rasselas is quiet and unassuming, but also a highly trained and deadly killer. He is by Shad Jehan out of Galietta. His color is "Golden with darker patches. Eyes Amber. Nose blue-black."
Both Calder and Behrens did classified work during World War II, then in the late 1950s went to work for a Mr. Fortescue at the Joint Services Standing Intelligence Committee (External Branch), more often known as JSSIC(E). In one story, the Prime Minister recalls his predecessor telling him that "E" Branch takes on the jobs "so disreputable" that no other agency will handle them. The cover of Mr. Fortescue is that of bank manager at the Westminster branch of the London and Home Counties Bank. As one adversary refers to them bitterly just before dying, both Calder and Behrens are "middle-aged cut-throats"; by the time the stories end, however, they have grown old but not noticeably softer or less capable.
Rasselas, however, in "A Prince of Abyssina", is killed by a German war criminal intent on killing Mr. Calder. After rescuing his friend, Mr. Behrens then helps Mr. Calder dig a
Undertones.
In most of Gilbert's work, which seems urbane, ordered, and placid on the surface, there are grim undertones and hard edges not far below. In "A Prince of Abyssinia" Colonel Weinleben signals Mr. Calder that he is coming to kill him. "Why?" asks Mr. Fortescue.
Later Colonel Weinleben takes up residence at the Seven Gables Guest House, where he goes birding and is "particularly nice with Mrs. Farmer's two young children."
"Michael was an exceptionally fine storyteller, but he's hard to classify," said one of his British publishers after his death. "He's not a hard-boiled writer in the classic sense, but there is a hard edge to him, a feeling within his work that not all of society is rational, that virtue is not always rewarded.".
Radio plays.
BBC radio plays, 14 unpublished, two published: