A buyer offered X for a building, which was accepted by the seller. The building had a mortgage, Y, which was greater than X. The terms of the purchase contract called for the building to be delivered "free and clear of all mortgages, liens, and other encumbrances," and the understanding was that the seller was supposed to pay off the mortgage by making up the remaining mortgage balance, Y-X.
Seller used only X to pay down the mortgage, which had a remaining balance of Y-X. Buyer doesn't want the building with the Y-X mortgage remaining on it, wants to cancel the deal, and get his X back.
What is the name of the tort that the seller has committed? What rights and remedies does the buyer have?