I'm trying to find the title of an old film about late 40's early 50's about a woman whose parents have died in the war, and whose inheratance is being stolen by a relative by sending her mad. Her doctor though discovers something is wrong and ends up chasing the relative into the swamp land where he dies by being sucked into some quicksand.

Dark Waters (http://www.tcm.com/tcmdb/title.jsp?stid=72331)