If this is a basement bathroom, you need to remove the sheetrock and see what is going on behind the wall. Most likely you have a cracked foundation and the water is pooling on this side of the house. It looks like you also may have a pretty bad mold situation behind that wall. Plenty of fans to the outside, and some bleach sprayed on anything black will at least help to control the spreading of mold through the home. And always wear a fine particulate respirator.
Or call in a professional to fix it....worth the $$ in my opinion.
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