truck to camper power cord trying to melt

I went to my camper last night to check inventory for our next trip. The camper battery was almost dead and it was cold inside the camper. Therefore, I backed the truck up to the camper and plugged the camper to the truck so I could have brighter lights inside and to run the furnace for about ten minutes. Once it warmed up a little, I went out to unplug the cord from the truck and the connection was very hot and when I unplugged it, a little smoke came out. One of the contacts had melted some of the plastic away. I waited a few minutes and plugged it back in and all the lights and everything seemed to work fine. Why did it get so hot and did I possibly damage anything? Is there anything I need to do? Thanks.