Can a mortgagee recover more than the amount due under their mortgage?

For the defendants it was urged that, in any event, the plaintiffs were not entitled to recover more than the amount unpaid under their mortgage, and as it was not shown what that amount was, they could not succeed. In my opinion a wrongdoer cannot inquire into the state of the accounts existing between the mortgagor and mortgagee. If the damages recovered exceed the amount due upon the mortgage, the mortgagee would be trustee of the surplus for the mortgagor. There must, however, be some portion of the mortgage debt remaining unpaid at the time the action is brought to justify a mortgagee in commencing an action, for his right to sue depends upon his having an interest in the property (Brookfield v. Brown, 1893 CanLII 54 (SCC), 22 S.C.R. 398). As I have already pointed out, the plaintiffs put in no evidence to show that anything remained unpaid on their mortgage. They, however, sue as mortgagees and produce their registered mortgage. They also allege that by reason of the removal of the dwelling the value of the land without the dwelling is not sufficient to pay the plaintiffs’ mortgage and prior encumbrances.