抽丝剥茧 (抽絲剝繭) chōu sī bāo jiǎn

chōu sī bāo jiǎn set phrase to spin silk from cocoons; to make a painstaking investigation
Domain: Idiom 成语
Notes: (CC-CEDICT '抽絲剝繭'; Guoyu '抽絲剝繭')