Like many other middle-class mortgage-payers, Mark and Star King jumped at the chance to make some money out of their home by renting it to holidaymakers through the popular travel website Airbnb.
The young Canadian couple bought their three-bedroom house in Calgary's fashionable Sage Hill for £217,000 ($436,610) in 2010, and were raising their two sons Vincent, 5, and 1-year-old Oliver.
So when a local man got in touch offering £435 ($875) to hire the house for a weekend for four relatives arriving in town for a wedding, they were quick to take up his offer. Any doubts they might have had at handing their house keys to a stranger ended when a well-dressed man arrived, who nodded judiciously as they ran through minor rules about not smoking or wearing outdoor shoes inside. "You have a beautiful home," he told them. "God bless you."
Soon after the Kings left the house, however, a bus arrived and 100 people poured in for what has since been described as "the craziest party this city has ever seen".
Police called it a "drug-induced orgy" that lasted two days and estimated the damage at £40,000 ($80,482).
The first the Kings knew was on Monday morning when they received a text message from a worried neighbour, asking what was going on at their house.
They rushed back but, under property laws in Calgary, landlords cannot enter a building without prior notice, so they had to wait for the party-goers to leave.
Mr King, who works for a Christian charity, told The Telegraph: "When we got there people were on the porch telling police to 'F off' and taunting them. It took my wife begging and pleading with some wasted girls through the glass for an hour before anyone would come out. We saw about 20 people file out, which was the left overs. A lot of them had passed out."
Inside was a scene of carnage where people had been taking drugs, including ecstasy, cannabis, and crack. There was vomit on the walls, condoms and women's underwear on the stairs, broken glass and crockery everywhere, barbecue sauce all over the 8ft-high ceilings, and a foul stench in the air.
The children's bedrooms had not been spared, with toys broken and Vincent's artwork destroyed.
Mr King said: "I felt shock and horror. My son's toys were in the midst of trash and condoms. We felt violated. We had trusted our home and all our possessions to this person, and took them at their word after doing what we thought was due diligence.
"To see everything so central to your lives defiled like that does a psychological number on you."
Mrs King, 29, an artist, described how a dazed young woman was wandering around barefoot on broken glass. She gave the woman a pair of her own shoes just to get her to leave.
Mrs King told The Telegraph: "I left my home in such immaculate condition. It was so clean and tidy. It was gorgeous and now it looks and smells like a garbage can.
"This was our sanctuary and we had worked really hard at making it home. Now I can't stand being in it. At this point it's not my home.
"There was gunk all over the walls and our feet were sticking to the floor. I don't want my baby crawling on that floor. We don't want to touch anything because everything's so filthy."
Items left in the house included a half-eaten birthday cake and a "Happy Birthday" balloon. According to neighbours, the bus arrived at the house shortly after the end of a major ice hockey game in Calgary.
Amid the damage, the floors and ceiling will have to be replaced, and a biohazard team has been sent in.
Mr King said: "Everything has to be treated as biohazardous material because of the bodily fluids. It all has to be sanitised before they can even put it in a landfill.
"Our clothes were locked in a wardrobe but we can't get them out until the fumes have gone."
Attila Horvath, a Calgary police constable, said: "I couldn't believe that someone could do that in three days to another person's home. I have never seen anything like it. This is disgusting."
Police said they will seek to charge the man who rented the house with mischief to property.
Airbnb began in San Francisco in 2008 as a way of helping people at a conference to find temporary accommodation.
The company has since become a travel industry juggernaut and was recently valued at $20 billion.
It has one million properties listed in more than 190 countries allowing guests to stay in everything from luxury villas to tree houses, or even a cable car in the Alps.
People who list their homes for rent are known as "hosts". Both hosts and guests write reviews about each other, helping to build up trust.
The Kings said Airbnb had been "extremely helpful" and were putting them up for free in another house during the three months it is expected to take to clean theirs.
They will be covered financially by the company's "Host Guarantee" which offers insurance "in the rare event of guest damages which are not resolved directly with the guest".
Mrs King, 29, is a dual British-Canadian citizen. She and her husband planned to relocate to London in 2016, putting rental income from the Calgary property toward the move.
Mrs King added: "I think it could happen to anybody, but a bolt of lightning could happen to anybody. Saying yes to the wrong people and not knowing, it's a freak situation."
In a statement Airbnb said: "We have zero tolerance for this kind of behaviour and our team is working quickly to make this right.
"We have banned this guest from Airbnb, and our Trust and Safety team will offer its full assistance to law enforcement in any investigation of this incident."