Where does the black wire with the red stripe go to- positive or negative?

Recently bought this truck. Battery & cable have been getting increasingly corroded. I took them off to clean them both. A wire slid off, but I didn't notice it at the time. I think it goes to the negitive side, but just want to be sure. Either way the truck won't crank now. Both neg & positive have 2 extra wires coming off the connector. I've never encountered this set up before. I'm lost.

Thanks!