People
Some things can only be seen in the shadows.
— Carlos Ruiz Zafon

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The line reverses the usual association between visibility and light. Shadows become a condition for noticing certain things, rather than simply an obstacle to sight. Read figuratively, it leaves room for understanding that emerges through obscurity, uncertainty or attention to what is less exposed.
Context reviewed