Un secreto vale lo que aquellos de quienes tenemos que guardarlo.
This is the first sentence from the first chapter of La sombra del viento (madera labrada was from the introduction) -- probably not a good portent of my success in the chapter. I can't figure out what the construction means here.
A secret is worth that which they of who we have to keep it.
A secret is worth that which something of we who have to keep it.
That doesn't make sense. What's going on here? I need an explanation of how aquellos and quienes are functioning in the sentence.