The Facts of a Case Heard by the Supreme Court

Short Answer

The facts of a case heard by the Supreme Court of Canada are as follows: Mr.and Mrs.H were induced to sign a mortgage in favour of M.C.R.Ltd.by Johnston,a man living with their daughter.Johnston led them to believe that the document was an unimportant amendment to an existing mortgage when,in reality,it was a second substantial mortgage on their home.Neither read the document nor questioned it.When the payments were in arrears,the mortgagee took an action for foreclosure (to take their home).Mr.and Mrs.H.pleaded non est factum.Would this defence succeed? If so,why; if not,why not?