Ta.ylob, J.
The reaper in controversy in this action was, as appears from the evidence, in the possession of Taylor Bros, at the time the same was seized by the deputy of the respondent, and it was in their possession as owners and mortgagors. There is nothing in the evidence which shows that, as to this reaper, the Taylor Bros, or Towne had any possession of it as the agents of the plaintiffs, for sale or otherwise. It shows nothing further than that the Taylor Bros, were the owners in possession, subject to the mortgage of the plaintiffs. As mortgagors of the property in possession they could not bind the mortgagees by any acts or admissions concerning the title, and, so far as the rights of these plaintiffs were concerned, their positive acts or omissions to act when the deputy sheriff made his seizure could not estop the plaintiffs. But if the *457Taylor Bros, had been in possession of this reaper as the agents of the plaintiffs, with full power to sell and dispose of it for the plaintiffs, claiming no title in themselves, we fail to find any evidence in the record in this case which would estop the plaintiffs from claiming title .to this reaper as against the defendant. Certainly the plaintiffs cannot be estopped, by any acts of their agents except such as were done or omitted in the line of their duty and within the scope of their authority as agents of the plaintiffs. We have certainly very grave doubts whether the agents to sell the plaintiffs’ property would be acting within the line of their duty, if, when a sheriff came with a writ to seize their own goods, they directed him to seize the goods of their principals. Such an act would seem to be without the scope of their authority, and not binding upon their principals. If the agents could not bind their principal in such a case by directing the sheriff to seize his goods, their mere silence or omission to act at all when the officer seized the goods of their principals, could not affect their rights. See Emmons v. Dowe, 2 Wis., 322, 364, 365; Kingman v. Graham, ante, p. 232; Ford v. Smith, 27 Wis., 261, 267; Main v. Bell, id., 517. In order to create an estoppel in favor of an officer seizing property upon a writ, against the real owner thereof, such owner or his authorized agents must have done or omitted to do something which induced the officer to act differently from.,what he would have otherwise done, and it must also further appear that the assertion of the real title will jeopardize the rights of the person in whose favor the writ is issued, contrary to equity.
If a seizure of the wrong property upon a writ of replevin were induced by the real owner, that might be a good defense to an action for the mere seizure; but if the owner afterwards notified the sheriff of his title, and demanded the return of the property, the sheriff would be a wrongdoer for not returning it, unless he could show that it would be prejudicial to the rights and interests of the person in .whose favor *458such property was seized, to permit such, return thereof. This seems to be the reason which has induced the courts to hold that under certain circumstances a receiptor of property seized upon a writ cannot be permitted to set up that the property so seized and receipted for was not in fact liable to such seizure. See Perry v. Williams, 39 Wis., 339, 343. In that case Justice Lyou, in delivering the opinion of the court, says: “ It is conceded on all hands that a receiptor who conceals from the officer his ownership of the property, and suffers it to be attached as the defendant’s, thereby preventing the officer, perhaps, from attaching other property, is precluded, when sued upon the receipt, from setting up property in himself.” And in Ford v. Smith, the former chief justice says: “And the proposition, too, that there would be an estoppel growing out of a mei’e levy made in consequence of such statements, although authorized, when the sheriff was informed of the truth, and notified not to proceed, before sale, is untenable. The sheriff does not, by the levy alone, acquire the position or rights of a purchaser for value without notice.”
These cases, we think, establish the position that the real owner is not estopped from asserting his title to property seized by an officer upon a writ, notwithstanding such seizure was induced by his acts, if after such seizure the officer is notified of the real owner’s title, and directed not to proceed; unless, as above stated, it be «further shown on the part of the officer that it would be prejudicial to the rights of the party in whose favor the seizure was made, to permit the property to be returned to the real owner. After the officer has notice that he has taken the wrong property, he cannot lawfully refuse to return it to the real owner, unless such owner would be estopped from asserting title to the same as against the party in whose favor the writ issued. In this case there is no evidence which establishes any equitable estoppel in favor of Dahling, the plaintiff in the writ of replevin, against these plaintiffs. He was in no way misled by them or by their *459agents. He must be supposed to have bad knowledge of the identity of tbe property owned by himself, and the evidence shows that he was the real cause of the mistake made by the sheriff. He pointed out the reaper which the sheriff seized, as the reaper he owned and the one described in the writ, without any misleading* by the plaintiffs or their agents. There can be no estoppel of the plaintiffs as against him. Had the sheriff delivered the reaper to Dahling in pursuance of the judgment in the justice’s court, there could be no doubt of the right of the plaintiffs to recover of him the value thereof. He could not set up his own mistake as a defense to their action.
But it is unnecessary to pursue this subject further, as the question of estoppel was not put in issue by the pleadings in the case. It appears well settled by the decisions of this court, that an estoppel must be pleaded in order to enable the defendant to avail himself of it on the trial. See Gill v. Rice, 13 Wis., 549-554; Waddle v. Morrill, 26 Wis., 611; Wait’s Law and Practice, 1090. In this case no estoppel was attempted to be set out by the defendant in his original or amended answer, and the second answer of the defendant, which attempts to justify the taking by the deputy of the respondent, virtually admits the title of the plaintiffs, and places the defense solely on the ground that the property in question was the identical property described in his writ of replevin, and he was therefore justified in taking and holding the same on said writ, notwithstanding it was the property of the plaintiffs. No estoppel having been set up in the defendant’s answer, and the plaintiffs having excepted to all that part of the judge’s charge which submitted that question to the jury, it was error to do so. For these errors the judgment must be reversed.
As there will probably be a new trial in this case, we are constrained to add that, upon the evidence as it appears to us in the record, we think this was a very proper case to apply the *460rule laid down by this court in Churchill v. Welsh, 47 Wis., 39; and that if the jury find that the officer, as soon as he ascertained that he had made a mistake in seizing the wrong reaper, tendered the same back to the mortgagors from whose possession he took it, and left it on their premises, and thereafter asserted no claim to the possession of the same, such tender should have mitigated the damages to merely nominal, unless the evidence shows that the plaintiffs have suffered other damages beyond the mere value of the reaper by reason of the seizure thereof by the respondent’s deputy. If no tender be shown previous to the commencement of this action in the justice’s court, the offer then made'to return the property and pay the costs should be considered; and if the evidence shows that the seizure was made in good faith by the officer, supposing he was taking the property described in his writ, and he shows that the reaper was in as good condition when he offered in his answer to return the same, as it was when he took it from the plaintiffs’ possession, then the damages should be nominal, unless, as said above, the proofs of the plaintiffs show that they have suffered some other damage by the taking and detention, beyond the mere value of the thing taken; and in such case the damages should be limited to the amount sustained beyond such value.
By the Court.— The judgment of the circuit court is reversed, and the cause remanded for a new trial.