Why adapt a murder mystery if you don’t care about the mechanics of the story to begin with? I ask myself this often when it comes to the work of Agatha Christie, and the question was ever-present throughout the three-part series “Towards Zero” on BritBox.

I’ve been making my way through Christie’s books for the past year or so (70-plus novels, not even counting the short stories) and the qualities that make her such a fun read — or fun listen; the official audiobooks narrated by actors are terrific as well — are rarely in evidence when it comes to newer film and TV versions, which rarely capture her voice. They’re usually too serious and given a “prestige” patina that feels simultaneously undercooked and overdone.

Christie wrote until her death in 1976 (well, almost; her last novel was published in 1973) and her books incorporated subtle details reflecting the changes happening around her. And yet when those same stories are adapted into TV or film, we’re invariably trapped in the 1930s. Specifically, a glamorously imagined version of the ’30s. That’s true here as well. “Towards Zero” was published in 1944 but the setting has been changed to 1936. That’s my first beef.

The original book opens with Christie dropping breadcrumbs that introduce seemingly unrelated characters — whose importance will be revealed later — before getting to the main players at hand. All of that prologue is gone in this version, which makes sense. Condensing a novel isn’t easy. What to keep in? What to leave out? But too many changes to the story itself are fundamentally at odds with the spirit of Christie’s writing. The result is airless. Aimless, even.