a puff of smoke and now nothing 69 valiant electrical issue

weird as he unhooked everything and rehooked everything with the battery unplugged. from looking at the picture, there was a positive and negative cable (red/ and black) that were screwed in. Could he have rehooked them backwards? if he did..then that would have gone to the fusable link? The light meter lit up when i checked for power to it with the link removed....