Halo 3 help?

Question

Recently I have been trying to get all of the 13 Halo 3 skulls. I have 12 of the 13 skulls. But the catch skull is not showing up. I havn't destroyed the wraiths or anything. I know I have to beat the game on normal. But do I have to do the campain in the right order. Or can I do The Ark first. Or Crow's Nest last? As long as I complete all the missions? Or do I have to start at arrival and end at halo.

HELP ME PLEASE!!!

Answer 1

you have to finish the level from the very beginning