Welcome BeverlyAnn, to the best darn DIY'r site on the web.
If your furnace has a flue (vent) pipe that runs up to the roof, the water may have entered through that. Check to see if there is a cap on the top of the pipe, if not, then the water definately came from that location.
If your furnace is a high efficiency unit (PVC) vent out the side wall, then the water most likely came from the coil in the furnace plenum, (condensate from the AC evap coil) if this is the case then you have a plugged drain line on the coil and water is overflowing the catch pan around the coil.
When its all said and done there is usually more said than done
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