(Spoilers)
Great film, the ressemblance between his flat and jail cell in the end is very interesting. It makes you wonder whether is it because his new life was already feeling like a prison or whether is imprisonment could be seen as a new start as well. I do have a theory about the twist. After a bit of thinking I came to the conclusion that the wife wasn’t in on it, only the husband. It started from the diner alvaro hosted. He hosted it on purpose to give ideas to his neighbours about robbing the old man, which worked but only on Enrique. From the moment he went for diner, he learned about the safe, the code and the fact that Alvaro himself knew all that too. Not only this, but as mentioned by his wife you can see his old habits are kicking in like his drinking. She did mention Enrique getting in trouble in the past, which seem a reasonable assumption that he robbed in the past and the financial troubles were an excuse for going back to it. Alvaro gave him a golden opportunity and a perfect scapegoat for the perfectly presented plan.
The funny part is that the only good thing alvaro ever did for his neighbours was to tell Irene to stay with his husband, support him. Which backfired pretty badly for alvaro when she indeed stuck with her husband after the robbery. There’s definitely a certain irony and karma in the end.