It has been nearly 12 years since Madeleine McCann vanished from a holiday apartment in Portugal, and police are still no closer to solving the mystery.
More than £11 million has been spent and hundreds of people were spoken to.
But there is one suspect who police never got to interview.
In 2013, Portuguese police stumbled across a new lead and began investigating a man who had been working as an employee at The Ocean Club resort in Praia da Luz not long before Maddie disappeared on May 3, 2007.
The employee was Euclides Monteiro, an immigrant who had been fired from the beach club for stealing from guests.
Police say Monteiro may have been motivated by revenge against his former employer after being sacked.
Theories circulated that the 40-year-old was a heroin addict and may have stumbled across Madeline while attempting to burgle the McCanns' room, according to the Telegraph.
In 2013, Portuguese newspaper Correio da Manha said, "The motives that could have caused the ex-employee to kidnap the youngster are still being investigated. The suspect could have taken the child to commit a sex crime before killing her. But he could also have committed the kidnap as a form of retaliation against the Ocean Club."
After being identified as a suspect following suspicious phone records, police were set to question Monteiro.
But officials never got to talk to the ex-employee because he died in a tractor accident in 2009.
Nelson Rodrigues, a barman and waiter who worked alongside Monteiro in 2006 described him as a sketchy character.
"On the surface he was a nice guy but there was something not right with him," Rodrigues told the Mirror back in 2013.
"He would turn up to work with bleary eyes, sometimes he didn't seem like he was all there.
"And things were going missing about that time – laptops, jewellery, mobile phones, anything that was lying around."
Monteiro, originally from Cape Verde islands off West Africa, was convicted of theft in 1996 but escaped deportation after he was pardoned.
The now-deceased man was at the time living in Lagos, just a 15-minute drive from where Maddie disappeared.
A British ex-pat reported a possible sighting of a girl who looked "remarkably like Madeleine" being dragged along the road to Lagos the morning after she went missing.
Monteiro was not originally questioned by authorities as he no longer worked at the Ocean Club at the time, however, his widow Luisa was then questioned about the 40-year-old's suspected involvement.
"It is disgusting they are now looking for a dead man as a scapegoat," she told the Mirror back in 2013.
"It's very easy to blame someone who can't defend themselves anymore.
"My husband would never be capable of committing such a crime."
Searches for Maddie's body were carried out based on new evidence but nothing was ever found.