On smaller Japanese trucks that I've had, some of them had a vent in the back of the cab, hidden by the bed. I discovered some water under the passenger rear seat - in the sunken area and above that by the hinges. Not sure where it would have come from - it has rained a lot recently and I may have had a window opened but didn't see any evidence of this on the seat itself. I also may have had a bottled water under there that leaked - not positive.
Anyway, other smaller trucks I've owned have had a vent in the rear cab wall - sort of a one-way thing to allow fresh air to circulate through. Does anyone know fi the Dodge QC has anything like this? Can't seem to find a pic in the service manual nor a mention mof anything but I'm puzzled as to where this water would have come from.