It appears that on a former trial of the cause, defendants admitting the execution and existence of the contract sued on, bad pled by way of defense and offered evidence tending to sbow that there was a contemporaneous oral agreement and by virtue of wbicb defendants were to be released of the obligation of the written agreement if they failed in interesting certain designated persons in the enterprise witbin ten days from its date. Tbis claim having been established, there was judgment for defendants wbicb on appeal was set aside, the Court being of opinion that the parol evidence on which the defense was based was incompetent as being in conflict with the terms of the written agreement. See Building Company v. Sanders, 183 N. C., 413. the opinion having been certified down, defendant was allowed to amend bis answer so as to allege that the paper-writing sued on bad never become the contract of the parties, but that same bad been delivered with the express understanding and agreement, that it was not to bind the parties or become operative as a contract unless and until they could witbin ten days interest certain men of means in the enterprise. There was evidence by defendant in support of tbis position, and at first received, but later bis Honor, being of opinion that the evidence was incompetent as violating the written contract, same was withdrawal by him over defendant’s objection, and plaintiff thereupon recovered judgment. It is held wdtb us that “while the express terms of a written contract may not be varied by a contemporaneous oral agreement, it may be alleged and shown the delivery of the written instrument was on condition that the same should not be regarded ás a contract until the happening of some contingent event.” In Bowser v. Tarry, 156 N. C., 38, the position is stated as follows: “That although a written instrument purporting to be a definite contract has been signed and delivered, it may be shown by parol evidence that such delivery was on condition that the same was not to be operative as contract until the happening of some contingent event, and tbis on the idea, not that a written contract could be contradicted or varied by parol, but that until the specified event occurred the instrument did not become a binding agreement between the parties.” And so expressed, the principle has been repeatedly approved and applied in our decisions. Thomas v. Carteret, 182 N. C., 374-378; White v. Fisheries Co., 183 N. C., 228; Mercantile Co. v. Parker, 163 N. C., 275; Garrison v. Machine Co., 159 N. C., 286; Pratt v. Chaffin, 136 N. C., 350. And. we may not allow the argument of appellee that the contrary is the law of the case by virtue of the former opinion. That is a position that prevails *332when the pleadings and evidence are the same or practically so and where there is a substantial change in both there is error and .this will be certified that there may be a new trial had of the cause.
New trial.