Ins and Outs of the Matter
(The). All the details, both direct and indirect.
“If you want to know the ins and outs of the Yankees ... I know all their points, shape, make, and breed.” —Haliburton.
Sometimes the “Ins” means those in office, and the “Outs” those out of office, or in Opposition.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894