do not leave a stone unturned

松本清張の "Points and Lines" を読みました。以前取り上げた表現　"leave no stone unturned" (9/11/2005)が次の個所に出て来ました。
As you say in your letter, if it is essential that Yasuda be situated at the scene of the double suicide on the night of the twentieth, then it would be impossible for him to have arrived at Sapporo by the Marimo Express on the twenty-first. If there is no evidence that he used planes then I'm afraid we have overlooked something, while taking other facts for granted. This is what I meant by an ancient story of the old woman and her winter jacket. Please do not leave a stone unturned.
点と線を読み上げました。最後は犯人夫婦の心中で終わったのはもっともらしく良かったと思いました。