Judy Anderson (Anderson) appeals from a judgment notwithstanding a jury verdict which awarded $93,261.50 in an action for wrongful death and destruction of property. The jury found defendant-appellee Melvin Kroh (Kroh) liable for negligent omissions resulting in a fire which killed Anderson’s ten-year-old son Ricky and destroyed her personal property. In a memorandum opinion the court reported that it put aside the verdict because it could find no evidence of negligence or proximate cause. We reverse.
In March 1977, Anderson rented from Kroh a mobile home situated several miles west of Mandan. Kroh lived on the same property in a building to the north of the Anderson trailer. Anderson had learned of the mobile home through a want ad for renters. Anderson made a deposit of $200 and agreed to pay $250 per month pursuant to what apparently was a month-to-month lease.
From the time she moved in until May 28, 1978, Anderson had no trouble with the trailer’s water heater except for one occasion. In October 1977 the flame in the water heater went out because the propane supply had been used up. The serviceman who delivered a new stock of propane relit the heater. Kroh owned the home for almost five years before Anderson rented it and, during that time also, the water heater functioned normally.
On May 28, 1978, Anderson discovered that the trailer was without hot water. At approximately noon she sent her twelve-year-old daughter, Shari, to notify Kroh that the water heater was not working. Kroh arrived, according to conflicting testimony, sometime between about 1:00 and 2:30 p.m. Kroh admitted having to light the heater at that time. Shari observed that Kroh needed “three or four matches” to start the flame, and both Kroh and Anderson agreed that he was there some ten minutes. However, Kroh claimed he had no difficulty lighting the heater. Anderson, Shari and Marjorie Pulkrabek, Anderson’s hairdresser who was present at the time, all testified that Kroh returned to the trailer shortly after leaving the first time. Anderson said he worked again on the heater and Shari said “he re-lighted it.” Kroh denied that he came and lit the heater a second time.
Whether it was once or twice that Kroh went to the trailer, he left Anderson with instructions to leave the door to the water heater compartment open.1 This was in order to dry up the dampness which Kroh detected in the compartment. This dampness was noticed by Anderson, too, after Kroh left. During that afternoon and evening Anderson observed the flame burning to the side of and down from the water tank. She stated that the flame was “reddish-orange.” A friend, Wayne Schier-meister, testified that he looked at the water heater in the evening of the same day. The flame, at that time, “was just kind of hanging in there fluttering.”
*361Though Anderson and Schiermeister observed the various irregularities in the flame, they stated that they knew nothing of how the heater should operate. They were not alarmed because they assumed Kroh had competently taken care of the matter. Indeed, Kroh claimed a fair amount of experience with propane heating devices through his employment. He had always taken care of necessary repairs, and Anderson said that she made no attempt to take up this role. However, Kroh testified that all he had done was light the heater, even though he noticed dampness in the compartment. He examined a faucet on the heater for leakage but otherwise made no investigation, and specifically stated that he did not check the flue.
Schiermeister and Anderson left the trailer at about eleven that night to meet friends. Remaining at home were Anderson’s four children, including Shari. When Anderson returned at about one o’clock in the morning, the trailer was on fire. Ricky did not get out of the house as did the other three children. He had gone to bed in his room and that is where he was found by the firemen. The trailer was a total loss, as was all of Anderson’s personal property.
Schiermeister, Anderson, and one of Anderson’s friends who was at the scene, Barbara LaFountaine, all testified that initially the fire was burning on the back portion of the trailer where the water heater was located. Richard Radspinner, Chief Deputy and Chief Investigator for the State Fire Marshal’s office, testifying as an expert, stated that the “basic area of origin of the fire” was here determinable “without any great degree of difficulty.” According to Radspinner, “the fire did start in the area of the water heater in the trailer house.” In his official report, Radspinner attributed the cause of the fire to “a malfunction of either the controls or the burners of that water heater.” However, the unit was too badly damaged in the fire to permit direct examination. Radspinner continued:
“I might elaborate on that by saying that basically there are four things that will cause a fire, particularly in the house or any building that is inhabited. One would be a heating system. Of course, one is an electrical system. Thirdly, in general is a human error-accident-and the fourth we describe as a deliberate act. Together with the heating system, we generally consider a heating system in this area to be a gas fire, an appliance, and we fairly well lump the gas fired water heater in as part of that rather than being a separate thing. Within that area of origin there were no other sources of ignition, no evidence of any other sources of ignition, no evidence of human error, accident, no evidence of a deliberate act, no evidence of an electrical involvement. We reduce then to the other source of ignition within the area of origin, which was the water heater.”
Radspinner’s testimony eliminating possible alternative causes was well corroborated by other witnesses.
Proceeding on the theory that an obstructed flue was responsible for the blaze, Anderson introduced evidence showing that a blocked flue can in fact cause a fire. There was testimony to the effect that an improperly operating flue produces certain symptoms, including condensation and dampness in the house or heater compartment, and an orange flame that flutters, burning downward and sideways for lack of oxygen.
The defense countered by showing that an orange flame can be due also to a shortage of fuel and that Anderson’s propane tank may have been almost empty. Kroh established that a clogged flue will produce soot at the bottom of the water tank and will foul the surrounding air with a pungent odor. Kroh stated that when he lit the heater he discovered no sooty deposits on the tank nor any strong odor. No one else testified on these points.
An experienced water heater repairman, Martin Gunsch, testified that when a heater’s flame goes out one should do more than merely relight it. He stated that “you should check the flue on any gas appliance you work on.” Direct examination of Gunsch was concluded with the following exchange:
*362“Q. Well, Martin, isn’t it enough simply if you are called because the water heater isn’t working, isn’t it enough to go-to just go and light it and walk away from it?
“A. Oh, no, Geez, you never want to do that.
“Q. Why not?
“A. Well, because it could be quite hazardous and you could light and your flue could be off, or else you could have a bad chimney, or else even if the water heater might have been-the valve might have been defective and therefore you are getting not the right mixture of air and gas so then therefore that could have been sooting a little bit and then you might not have enough draw up there and then it will come back down again, see.
“Q. Okay.
“A. Plus, you check it always to see if the valve shuts off because there is a safety on that also, just like your thermocoupler. The valve will come off too.
“Q. If the gas water heater goes out, then you are saying you should find out why it went out?
“A. Definitely.
“Q. You just don’t keep lighting it once and then twice and walk away from it?
“A. You light it, but you should have a reason why it went out. You should know why it went out.”
Another maintenance man testified on behalf of Kroh, and he too left the impression that checking the flue is a routine matter on any service call.
The rule followed by this court in reviewing a judgment notwithstanding the verdict is as follows:
“When ruling on a motion for a directed verdict or for judgment notwithstanding the verdict, the court must decide whether the evidence is such that, without weighing the credibility of the witnesses or otherwise considering the weight of the evidence, reasonable men could reach but one conclusion as to the verdict, or, otherwise stated, whether the evidence, viewed most favorably to the party against whom the motion is made, and giving that party the benefit of all reasonable inferences from the evidence, compels a result with which no reasonable person might differ.” Nokota Feeds, Inc. v. State Bank of Lakota, 210 N.W.2d 182, 187 (N.D.1973).
See also, Wall v. Penn. Life Ins. Co., 274 N.W.2d 208, 217 (N.D.1979). “Under our practice, verdicts are not readily upset.” Riebe v. Riebe, 252 N.W.2d 175, 177 (N.D.1977).
The facts clearly indicate the existence of a duty owed Anderson by Kroh. Section 323 of the 2d Restatement of Torts provides authority for this conclusion. It reads:
“One who undertakes, gratuitously or for consideration, to render services to another which he should recognize as necessary for the protection of the other’s person or things, is subject to liability to the other for physical harm resulting from his failure to exercise reasonable care to perform his undertaking, if (a) his failure to exercise such care increases the risk of such harm, or (b) the harm is suffered because of the other’s reliance upon the undertaking.”
Kroh’s attempt to light the heater, and Anderson’s reliance upon his actions, were sufficient to invoke this rule and to place upon Kroh a duty of reasonable care. Kroh gave no disclaimer or warning concerning his competence, and thus can be held to the standard to which others performing similar acts are held.
Kroh argues that the verdict was based on speculation and impermissibly attenuated inferences. In a negligence action the plaintiff must, of course, affirmatively prove lack of due care and causation. A plaintiff cannot rest on a presumption arising from the occurrence of an accident. Bismarck Baptist Church v. Wiedemann Industries, Inc., 201 N.W.2d 434, 440 (N.D. *3631972). Anderson expressly disclaims reliance on the doctrine of res ipsa loquitur and asserts that she has shown specific negligence. See Foerster v. Fischbach-Moore, Inc., 178 N.W.2d 258 (N.D.1970). She claims further that a causal relationship was reasonably deducible from the evidence.
Taking as true the evidence most favorable to Anderson, we must reject the lower court’s ruling that proof of negligence was insufficient to support the verdict. Martin Gunsch stated that when the flame in a water heater goes out, the cause should be determined. Kroh failed to do this not once, but twice. The possible implication of the dampness which Kroh admitted discovering, and the fact that the flame was abnormally colored, fluttering, and burning downward, make his omission even more significant in light of his experience and special knowledge. The record discloses that Kroh had been a mechanic for 15 years, for Northern Tank Line for five years, and for Coal Creek-hooking up heaters-and considered himself self-trained in the lighting and functioning of heaters and their thermocouples. It is not unreasonable to conclude, therefore, that, from the evidence before it, the jury could reasonably have found a failure by Kroh to exercise due care.
That Kroh was negligent does not settle the issue of liability, for a jury must be reasonable in its further finding that negligence was the proximate cause of the damage. Again, we believe a reasonable person could well conclude that Kroh’s misfeasance was a direct cause of the fire. In the opinion of an expert, Mr. Radspinner, the fire originated in the area of the water heater and the only plausible explanation was a malfunction of the unit. However, unlike the plaintiff in Bismarck Baptist, supra, Anderson submitted substantial evidence in addition to expert opinion. Corroborating Radspinner, several witnesses saw the fire at a relatively nascent stage and reported that its location corresponded with that of the water heater compartment. It was established that a blocked flue can cause a fire, and there is evidence implying that the flue was indeed blocked. Contrary evidence was received but does not authorize the court to set aside the verdict. Everson v. Partners Life Ins. Co., 268 N.W.2d 794, 797 (N.D.1978). Finally, it is noted that the record shows that up to May 28, 1978, there had never been any problems with the heater, that on May 28 the flame went out, that Kroh relit it twice with apparent difficulty, that the flame exhibited unusual and even disturbing traits the possible causes of which Kroh failed to investigate, and that on May 28 the trailer was consumed in a fire which started in the area of the heater. We cannot say that any reasonable person would be compelled to conclude that Anderson failed to satisfy the requirements enunciated in Bismark Baptist, supra.
The judgment of the district court is reversed and we remand for entry of judgment on the verdict.
ERICKSTAD, C. J., and PAULSON, SAND and VANDE WALLE, JJ., concur.. The door was not inside the trailer. It could be opened only from outside the trailer.