A maxim applied in the context of priority of mortgages. When there are successive mortgages of the same property, a mortgagee who is second or below in the order of priority may buy out (redeem) an earlier mortgagee. Any mortgagee may be redeemed by a mortgagee with a lower priority. If the matter is complicated and a court action is necessary, any person who might suffer in such an action must be made a party to it, i.e. the mortgagor and any mortgagees of lower priority to the mortgage being redeemed. Any person seeking to redeem by action must not only redeem any mortgages standing between him and the prior mortgage; he must also foreclose all subsequent mortgagees and the mortgagor. The principle does not apply to redemptions out of court.