Already checked the usual suspects, no water upfront, but extremely moist in the back seat carpets and floor...I had a plug missing in the rocker panel and there is no moisture from where the plug is and towards the driver....could water get kicked into panel from road and drip into car? Dont think its the trunk...plastic liner in there...where else?

It's your rear window seal leaking in the corners. Use some clear silicone caulk in the corners and it should stop it.

Did you check under the plastic cover over the vacuum and wires under the front carpets? Water from under the battery comes in through plugged holes or rusted spots and runs through a channel in the front to settle in the back floorwell. Drove me crazy till I found it and stopped with rust preventative and sealent.
Good luck

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Bob

03 ML320
99 C230K
85 300D 164K
93 190D 2.3 (sold)
62 220S (sold)
58 220S (sold twice -- a long story)

Also check your evaporator drain. I would suggest leaving the back carpets out for a few days after you have dried it out and then, after a ,see if it is wet. If it is not wet then it is the evap drain and obviously if it is wet it is coming in from outside.

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Jim

Ya...its only on one side of the car....drivers side rear area very wet...wet all the way u under the seats....all drains working...battery cable holes plugged....rear window prolly...ill check