not leave a stone unturned

Verb

leave no stone unturned (third-person singular simple present leaves no stone unturned, present participle leaving no stone unturned, simple past and past participle left no stone unturned)

1. (idiomatic) To search or investigate thoroughly.
   • “This case of police torture and murder is shocking. But this is not the first case and it is unlikely to be the last case until and unless the police conduct serious interrogations and investigations and leave no stones unturned,” said Sunai Phasuk, a senior researcher for Human Rights Watch.2021 August 25, Tassanee Vejpongsa, “Video sparks arrest of Thai police in drug suspect's death”, in The Washington Post, retrieved 26 Aug 2021
2. (figuratively) To perform a task carefully and thoroughly, not missing any step.
   • [He] left unturned no stone / To make my guilt appear, and hide his own.1697, Virgil, “The Second Book of the Æneis”, in John Dryden, transl., The Works of Virgil: Containing His Pastorals, Georgics, and Æneis. […], London: […] Jacob Tonson, […], →OCLC