Spoiler alert: Spoilers for Money Heist Part 5 ahead.
It looked like the gang had finally succeeded in moving the gold from the Bank of Spain to an underground stormwater tank using a very complex mechanical system.
However, just as the Professor (Álvaro Monte) and his team outside the bank are loading up the gold into trucks, police swarm the underground estuary and quickly handcuff the thieves.
After sitting in the back of a police van and noticing that very little is happening, the Professor gets suspicious, and it is soon revealed that it was not the police who found their hideout but another group of criminals.
So, who stole the gold in 'Money Heist'?
With just a little bit of deduction, the Professor and fellow mastermind Palermo (Rodrigo de la Serna) quickly realize that it is none other than Berlin's ex-wife, Tatiana (Diana Gómez), who has to be behind the crime, seeing as she is the only one who knew about the plan.
To make matters worse, Tatiana was joined by Berlin's son, and the Professor's nephew, Rafael, who is now dating his father's ex-wife.
Luckily, the Professor has Alicia Sierra (Najwa Nimri) on his side, and she quickly jumps in to locate Tatiana, Rafael (Patrick Criado), and the missing gold, while the Professor heads back to the Bank of Spain to be with his gang and negotiate with Colonel Luis Tamayo.
However, before heading back to the bank, the Professor hands Alicia a note that viewers soon realize is intended for Rafael.
What did the note say in 'Money Heist'?
During the final episode of the series, there is a flashback to Berlin (Pedro Alonso), the Professor, and Rafael all sitting in Madrid's Plaza Mayor and the Professor reveals that he witnessed the murder of their father (and grandfather), who was killed while robbing a bank.
"So, when you ask me why I choose to plan the heists, the answer is simple. To talk to him," the Professor tells Rafael, before adding that his father told him about his plan to rob the Royal Mint the night before his death.
Fast forward, and eventually, Alicia locates Tatiana and Rafael and passes him the note. While viewers don't see what is written, Rafael agrees to give the gold back with the promise that the Professor will send him a cut of the take.
"Are you sure he is going to give you your share?" Tatiana asks in the final moments of the show.
"Yes, it's a family matter," he responds.
Fans can only assume that the Professor reminded Rafael of that moment in Madrid and the importance of family — even if it is a family of thieves.
In the end, the Professor completes Berlin's final wish to rob the Bank of Spain, and the gang, down a few members, flies off into the sunset while the 90 tons of gold they stole was on the way to a secret spot in Portugal.
Watch all five parts of Money Heist on Netflix now.