The answer, as a defense to the action upon the ■ note and mortgage, sets up a contemporaneous parol contract under which defendants claim a partial discharge of the instruments. This contract shows an intention of both parties, in conflict with that embodied in the *355note and mortgage. It alters the conditions of the contract actually embodied in the- written instruments and defeats them. It is pleaded for the purpose of contradicting and varying the contract of the, parties set out in the note and mortgage. There is no principle of law more familiar than that one which declares that written contracts cannot be defeated or waived in this manner. Gelpcke, Winslow & Co. v. Blake, 15 Iowa, 387; Pilmer v. The Br. St. Blake, Des Moines, 16 id. 321; Warren v. Crew, 22 id. 315. The demurrer of defendant to the answer ought to have been sustained.
Defendant’s counsel, not disputing the doctrine above stated, argue that the case is not within its scope. It is claimed that the defense set up' in the answer is a partial failure of consideration and nothing more; that the contemporaeous parol contract pleaded specified the service to be rendered by plaintiff, which constituted the consideration of the note sued on, and that the failure in part of that consideration may be pleaded and proved as a defense to an action upon that instrument. It is true that a failure, a partial failure of the consideration of a note, may be pleaded as a defense to an action thereon between the original parties. Rev., ch. 76. But in the case before us the contemporaneous contract set out in the answer reaches farther than to create or specify a consideration upon which the note is based. It directly alters the terms of tlie contract embodied in the note and annuls, in part, its obligation. In the note, the defendants are bound to pay a sum of money without conditions. By the parol contract they are bound to pay that sum only upon the happening of a certain contingent event, and the note, by the terms of this contract, is declared to be defeated in part in case that event does not happen. It is very plain that the two contracts are in conflict and inconsistent; that the parol agreement varies and contradicts the note.
The judgment of the district court is Reversed.