leave no stone unturned

verb2

1. •
   To search or investigate thoroughly.

   • We have a lead inspector who has a global overview of the investigation and will have site handback in mind, although we won't leave any stone unturned. — 2021
2. •
   (figurative) 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