get to the bottom of the matter; investigate into an affair thoroughly;make a thorough inquiry into sth; inquire into the utmost details
❍ 我感到这样事情里面有问题，我建议～。I’ve smelt a rat in the matter. I suggest that we make a thorough inquiry into it.
穷源竟委qiónɡ yuán jìnɡ wěi
穷、竟：根究、追究；源：指水流的发源；委：末尾。比喻深入探究事物的始末。make a thorough, inquiry into sth., get to the bottom of the matter, go behind sth.