Another review has already given away the story, but I'll put in a SPOILER warning anyway.
This episode concerns the disappearance of a young high school boy. What starts out as a simple story reveals a very ugly sub-strata of society, with fourteen year olds having sex parties, including multiple partners. And the parents are totally unaware of it, largely because they don't seem to talk to their children.
The missing boy is at one point a suspected rapist, then a lover, then a hero. It's very well written because it manages to mix a disturbing story about underage sex and sexually transmitted diseases with a Romeo and Juliet plot that has a similar tragic ending.
The whodunnit revelation was cleverly hidden until the end. The ending itself is moving and so sad, because it was all so unnecessary.
A good story, a difficult episode to watch. Thought-provoking and gritty.