The two first laid eyes each other on the set of 2009 film, The Rum Diary, when the actor was still involved with longtime partner — and mother of his kids — Vanessa Paradis.
"It just felt like a little bit of on-set romance and nothing else, nothing more. They sort of flirted on the set and then they went back to their regular lives," says naughtygossip.com creator, Rob Shuter, in a teaser for REELZ's new docuseries, Johnny Depp & Amber Heard: Irreconcilable Differences.
In 2012, however, Depp, 55, and Paradis, 45, parted ways, and it didn't take long for the hunk to rush back to his former costar.
Before the two got engaged in 2014, there were already rumors of their allegedly troubled relationship — including claims of infidelity, abuse and violent fights.
"Bad things were coming out about Johnny and Amber's marriage before they were actually married. Their relationship was on the rocks before they were even engaged," says Shallon Lester, Star Magazine's deputy editor.
While Depp had been known as one of Hollywood's most talented actor for years, Heard, 32, quickly began making a name for herself in the industry.
"He has this young wife who's kind of becoming a pretty big deal. And I think that balance of power was probably a little difficult for both," says celebrity attorney Jill Stanley.
Depp and Heard seemed in love and inseparable for years, but as soon as the actress accused her husband of physical abuse, it all began to spiral.
"Almost as soon as it began, it fell apart," recalls Lester. "Their divorce is so contentious and so spread out."
"Abuse claims were brought up really, really fast," says Shuter. "She had text messages, she had evidence. So this got really, really nasty, really, really quick."
OK!Magazine.com readers know Depp vehemently denied the claims at the time and continues to do so. His exes and family members have also publicly defended him, though Heard has never changed her story.
Eventually, Depp paid Heard $7 million to close the case and end their marriage.
"I think they were in love, I think there was too much pressure, and like so many Hollywood couples, they just couldn't survive under it," concludes Stanley.
Johnny Depp & Amber Heard: Irreconcilable Differences airs Thursday, October 4 at 9:00 ET / PT.