As married spies, Michael Fassbender and Cate Blanchett lead a cast of duplicitous characters in Steven Soderbergh’s latest.

Black Bag centers on employees at the London-headquartered National Cyber Security Centre, leading some fans to wonder if the film is based on a true story.

So goes much of the crackling patter of “Black Bag,” Steven Soderbergh’s delicious marital drama cloaked as a sleek spy thriller. Lean and taut, the 93-minute “Black Bag” is more a sizzling amuse-bouche than full-course meal,