Sherlock gets called onto a kidnapping case that leads to a rather massive trafficking ring.
Like himself, he goes in alone and probably gets overwhelmed by the gang.

They don't believe that Sherlock isn't a cop, but instead they decide maybe this "pretty boy"/"pretty girl" will make them some money.

Sherlock eventually fights his way out/ is rescued.
Most of those in charge of this ring are arrested.

What follows is the court case and Sherlock has to deal with the fact that the children being scared/hurt disturbed him as well as his own suffering.

Lots of comfort from John and difficulty with testifying after a traumatic event.