灰の女 (hai no onna, Ash Woman, 1970) is a detective story by TAKAGI Akimitsu (高木 彬光) featuring his series detective, prosecutor KIRISHIMA Saburou (霧島三郎). I reviewed a collection which included one short story featuring Kirishima last year, Return of the Detectives ( 帰ってきた探偵たち, 1992). As with the stories in that collection, the public prosecutor is not quite an armchair detective, but still only involved at intervals in the investigation, most of which is of course carried out by the police. The narrative in this story switches back and forth between one of the suspects in the case (a suspect to the police, that is, not to us) and the investigators (either the police or Kirishima or both together).
SHIGA Sadahiko (志賀貞彦) is planning to leave his job as secretary for shady business owner IWAMOTO Gisuke (岩本義介) and run off with WAKISAKA Noriko (脇坂則子) the wife of the manager of a larger business, for which Iwamoto's company is actually a "tunnel" firm, a secret conduit for dealings they do not want on their own books. But the day after Sadahiko's resignation, Iwamoto is murdered. Noriko is a central witness in the case. She and her cousin had been sitting in the window of a café across from Iwamoto's office when the cousin thought he saw an attack through the window, and the two of them later discover the body. Noriko hides the fact that she had also seen her lover Sadahiko hurrying out of the building shortly after her cousin saw the fight.
Sadahiko however assures her that he has everything in hand and offers a convincing alibi to the police. He had been lured to the office by a false telephone call and had only entered the main workspace, not Iwamoto's private office; and there were witnesses outside to see that that was true. Still, the inspector on the case cannot help suspecting Sadahiko's immense confidence. Could the ash and wire remains found outside one of the office windows be a clue to some kind of trick? Noriko meanwhile, separated from her lover, is filled with panic about the crime and fear that Sadahiko may be the killer, especially when another murder follows.
I added the "locked room mystery" tag to this post, because Takagi treats the first murder as a locked room mystery. In many Japanese locked room mysteries, the holes are so large that they hardly deserve the name. In this case, the locked (or observed) room aspect only comes into play if you find plausible the police's assumption that it would be odd for a murderer to wait in a room until the people who are in the corridor outside have gone away before making his escape.
There are a couple of other implausible elements to the story, but on the whole it is well constructed and clued, with some ingenious elements. The main problem is that the actual killer is far too obvious. The detectives employ Ellery Queen level subtelty of reasoning, while ignoring the plain as day reasons why one suspect is almost certainly the criminal.