Plot comes first. The plot is the archictecture of your novel. You wouldn't build a house without a plan. If I wrote without a plot, it would just be a pile of bricks. Characters are your servants. They must serve your plot.
Barbara KingsolverLet me claim that Africa and I kept company for a while and then parted ways as if we were both party to relations with a failed outcome. Or say I was afflicted with Africa like a bout of a rare disease from which I have not managed a full recovery.
Barbara Kingsolver