At first, real estate agent Elise Stern thought it was a ghoulish prank. 

WARNING: Readers might find some details in this story distressing. 

Who would prop up two mannequins in a "fake murder" scene by the pool while she was trying to sell this Toronto mansion? 

The prospective buyers, who were being asked to pay $7 million for the sprawling luxury home, seemed annoyed by the stunt too. 

"It was very weird," police later wrote of the witnesses' discovery.

"They were far away and their heads were elevated and hanging on the railing leading into the pool." 

But as they stepped closer, a sickening realisation crept in. 

They weren't mannequins at all, but Barry and Honey Sherman, the billionaire owners of the property. 

The couple had been left in a gruesome position, seated side by side, with belts looped around their necks and fastened to the railing behind them. 

"They're dead!" Ms Stern wailed to the emergency dispatcher. 

The Shermans were well known philanthropists who mixed in Toronto's elite circles and ran one of the country's largest pharma corporations. 

But five years after their bodies were discovered, the murder of one of Canada's richest couples remains unsolved. 

Toronto police are no closer to an arrest, and a slew of detectives, lawyers and pathologists who were privately hired by the Sherman family are yet to crack the case.

Desperate for answers, the couple's son Jonathan is now offering a $35 million reward for any tip that leads to the arrest of his parents' killer. 

"Closure will not be possible until those responsible for this evil act are brought to justice," he said last month. 

But finding the murderer among an abundance of potential suspects may prove tricky. 

The mystery has turned siblings against each other, and confounded amateur sleuths. 

Even Jonathan himself has been accused of involvement in his parents' murders, a claim he has vigorously denied. 

The ruthless tycoon

No-one becomes a billionaire without making a few enemies along the way. 

Barry Sherman, famous for his ferocious rise through the pharmaceutical industry, once admitted that plenty of people wished him ill. 

"They hate us. They have private investigators on us all the time, trying to investigate. The thought once came to my mind, why didn't they just hire someone to knock me off?" he said in 2001. 

At his funeral, he was remembered as a fiercely loyal friend, father and CEO who relished a good fight. 

In 1974, he took the proceeds of the sale of his late uncle's pharmaceutical company and set up a ruthless version of the business. 

With Apotex, he undercut competitors by making generic versions of their drugs, making himself a very rich and very controversial man. 

He took advantage of Canada's pharmaceutical laws, manufacturing and selling a cheap version of a new drug years before its patent expired, and battling the outraged pharma giant in court. 

"If we're thieves, we're Robin Hoods," he liked to say when accused of stealing other people's ideas. 

But not everyone believed Sherman robbed big pharma to give to the poor. 

"He was a deplorable human being," University of Ottawa law professor Amir Attaran said days after Sherman's death.

"Canadians pay more for generic drugs than almost every other country. 

"He sought to manipulate our system to enrich himself and impoverish Canadian patients who used his drugs."

But Sherman did not just wage war against his business rivals. 

In the months leading up to his death, he was locked in a court battle with his own cousins. 

His four relatives claimed Sherman owed them a stake in Apotex because it had been founded with the sale of their late father's business.

While Sherman had financially supported them throughout their lives, they claimed that this was not a kindness, but a scheme to "make the cousins dependent on him, and to keep them from learning about their rights to the business".

Sherman won the case, and promptly withdrew millions of dollars that he had provided to his cousins. 

"I did everything I could to help them," Sherman said in 2017, just months before he died. 

The beloved philanthropist 

Despite his near-constant family feuds and litigation, Barry Sherman remained firmly ensconced in Toronto's elite. 

Those who knew him say this can largely be credited to his wife. 

The daughter of Holocaust survivors who was born in a refugee camp in Poland, Honey Sherman was warm, charming and universally beloved. 

A fundraising powerhouse, she sat on the boards of more than a dozen Canadian charities. 

While Barry remained a frugal workaholic, Honey enjoyed the trappings of their wealth, going on ski trips with friends and shopping trips with her sister. 

At his 50th birthday party, Honey presented her husband with a sports car covered in a huge bow. 

In front of their assembled guests, he demanded she return the car, which she did.

But by 2017, Honey had finally convinced her husband it was time to enjoy their fortune. 

They put their Toronto mansion on the market, and set about building their dream home. 

At an estimated cost of $30 million, Honey planned for a new estate in the posh neighbourhood of Forest Hill, featuring a central swimming pool with a retractable skylight and living quarters for staff. 

But the Shermans would never get to move in. 

The Shermans' strange final days 

In the days leading up to the murders, the Shermans' behaviour struck the people who knew them as a little odd. 

Honey failed to show up to a charity board meeting — highly unusual for the punctual and reliable philanthropist. 

The CEO of the charity sent her an email asking if she was okay, and she responded that she was "dealing with some stuff". 

Given her packed social calendar and the stress of building an ambitious new home, no-one gave it much more thought. 

The next day on December 13, the couple was spotted looking over blueprints for the new house at Apotex HQ before heading home for the evening. 

Barry sent one email that night to an employee about a minor work matter and then fell silent. 

The insomniac workaholic usually sent a string of emails into the early hours of the morning. 

This would be the last time anyone heard from the Shermans. 

He didn't show up for work the next day, but given the famously frugal businessman refused to hire a driver, personal assistant or bodyguard, his movements were always somewhat mysterious. 

On December 15, Elise Stern brought the prospective buyers to the house and let herself in with the key the Shermans had left her in a lockbox. 

She had been told that Honey would be on holiday in Florida and Barry would be at work. 

After taking the potential buyers on a tour of the home's five bedrooms, tennis court and sauna, she suggested a peek at one of the property's more luxurious flourishes. 

In the basement, the Shermans had added a pool and hot tub so they could swim even in the depths of Toronto's harsh winters. 

'There are people out there who would have a grudge against them' 

News of the murders rocked Canada. 

As police descended on the estate, a tangle of wild theories spread throughout Toronto's high society and pharmaceutical industry. 

There had long been whispers of tax havens and murky business deals. 

Had the couple fallen victim to a disgruntled employee or one of the many enemies Barry Sherman had made during his unmerciful rise to power? 

The day after the bodies were found, the Toronto Star reported that police were probing the possibility that Barry had murdered Honey before taking his own life.

The story outraged their children. 

"We are shocked and think it's irresponsible that police sources have reportedly advised the media of a theory which neither their family, their friends nor their colleagues believe to be true," they said in a statement.

Concerned that Toronto police were out of their depth, they hired their own experts, who went through the evidence and conducted a second autopsy of the bodies. 

There were no signs of forced entry, but the family pointed out that a window was found open and a door unlocked. 

Marks on the body suggested they had had their wrists bound with zip ties, and the pathologist concluded Honey had likely been killed in another part of the house and dragged down to the pool. 

Six weeks after their deaths, Toronto police ruled out Barry as a suspect and confirmed they were treating the case as a double homicide. 

"[They] were complicated people," Jonathan Sherman told police in documents later filed to a Canadian court. 

But as weeks drifted into months and the months into years, the case remained shrouded in mystery. 

On the fourth anniversary of their deaths, police released CCTV footage of the "walking man". 

A neighbour's security camera captured a person with an "unusual gait" who trudged through snow to and from the Sherman house at the time they were likely killed. 

But this lead, like all others, grew cold. 

Could a $35 million reward unveil the killer?

In the years since the murders, a schism has developed between Barry and Honey's children.

Their only son Jonathan told the Toronto Star in 2021 that he is no longer in touch with his sister Alex because she accused him of involvement in the crime. 

Just two weeks before his death, Barry had asked his son to pay back a $50 million loan to help him through some short-term cash flow issues. 

"I'm not going to kill my dad because he needs $50 million to get through a crisis," Jonathan told the Toronto Star in 2021.

In his will, Barry directed his trustees to evenly distribute his estimated $3.2 billion fortune among his four children. 

They have subsequently sold Apotex, razed the family home where their parents died, and sold off the block of land. 

Both Jonathan and Alex have separately employed private security guards to tail them wherever they go in case their parents' killer comes for them next. 

Toronto police have declined to comment on the accusations made within the Sherman family, saying only that "several persons have been implicated". 

"To date, there is no evidence to elevate any of the aforementioned parties to the status of a suspect," they said. 

On the fifth anniversary of the murders, the siblings issued separate statements, pleading for answers. 

"My parents deserved to enjoy the fruits of their labour," Jonathan Sherman said in December when he increased the reward to $35 million.

"I continue to miss my parents more than I can describe, and I am forever haunted by what happened to them." 

Alex made no mention of her brother as she paid tribute to their mother and father. 

"The horrific manner in which they were taken from us has been extremely traumatic," she said. 

"My heart is broken. My loss is immeasurable. My children have lost their grandparents. We miss their guidance, love, and wisdom."